Spring interconnect structures

RELATED APPLICATIONS

0001This application is continuation-in-part of patent application Ser. No. 09/205,022 filed Dec. 2, 1998 entitled “Lithographic Contact Elements,” and patent application Ser. No. 09/205,023 filed Dec. 2, 1998 entitled “Lithographic Contact Elements.”

BACKGROUND OF THE INVENTION

00021. Field of the Invention

0003The invention relates to an interconnection (contact) element suitable for effecting pressure connections between electronic components and is particularly useful for contacting semiconductor packages or for contacting a semiconductor directly.

00042. Description of Related Art

0005Interconnection or contact elements may be used to connect devices of an electronic component or one electronic component to another electronic component. For example, an interconnection element may be used to connect two circuits of an integrated circuit chip or including an application specific integrated circuit (ASIC). Interconnection elements may also be used to connect the integrated circuit chip to a chip package suitable for mounting on a printed circuit board of a computer or other electronic device. Interconnection elements may further be used to connect the integrated circuit chip to a test device such as a probe card assembly or other printed circuit board (PCB) to test the chip.

0006Generally, interconnection or contact elements between electronic components can be classified into at least the two broad categories of “relatively permanent” and “readily demountable.”

0007An example of a “relatively permanent” interconnection element is a wire bond. Once two electronic components are connected to one another by a bonding of an interconnection element to each electronic component, a process of unbending must be used to separate the components. A wire bond interconnection element, such as between an integrated circuit chip or die and inner leads of a chip or package (or inner ends of lead frame fingers) typically utilizes a “relatively permanent” interconnection element.

0008One example of a “readily demountable” interconnection element is the interconnection element between rigid pins of one electronic component received by resilient socket elements of another electronic component, for example, a spring-loaded LGA socket or a zero-insertion force socket. A second type of a “readily demountable” interconnection element is an interconnection element that itself is resilient or spring-like or mounted in or on a spring or resilient medium. An example of such an interconnection element is a tungsten needle of a probe card component. The interconnection element of a probe card component is typically intended to effect a temporary pressure connection between an electronic component to which the interconnection element is mounted and terminals of a second electronic component, such as a semiconductor device under test.

0009With regard to spring interconnection elements, generally, a minimum contact force is desired to effect reliable pressure contact to an electronic component (e.g., to terminals of an electronic component). For example, a contact (load) force of approximately 15 grams (including as little as 2 grams or less and as much as 150 grams or more, per terminal) may be desired to effect a reliable electrical pressure connection to a terminal of an electronic component.

0010A second factor of interest with regard to spring interconnection elements is the shape and metallurgy of the portion of the interconnection element making pressure connection to the terminal of the electronic component. With respect to the tungsten needle as a spring interconnection element, for example, the contact end is limited by the metallurgy of the element (i.e., tungsten) and, as the tungsten needle becomes smaller in diameter, it becomes commensurately more difficult to control or establish a desired shape at the contact end.

0011In certain instances, spring interconnection elements themselves are not resilient, but rather are supported by a resilient membrane. Membrane probes exemplify this situation, where a plurality of microbumps are disposed on a resilient membrane. Again, the technology required to manufacture such interconnection elements limits the design choices for the shape and metallurgy of the contact portion of the interconnection elements.

0012Commonly-owned U.S. patent application Ser. No. 08/152,812 filed Nov. 16, 1993 (now U.S. Pat. No. 5,476,211, issued Dec. 19, 1995), and its counterpart commonly-owned co-pending “divisional” U.S. patent application Ser. No. 08/457,479 filed Jun. 1, 1995, U.S. patent application Ser. No. 08/570,230 and U.S. patent application Ser. No. 09/245,499, filed Feb. 5, 1999, by Khandros, disclose methods for making spring interconnection elements. In a preferred embodiment, these spring interconnection elements, which are particularly useful for micro-electronic applications, involve mounting an end of a flexible elongate element (e.g., wire “stem” or “skeleton”) to a terminal on an electronic component, coating the flexible element and adjacent surface of the terminal with a “shell” of one or more materials. One of skill in the art can select a combination of thickness, yield strength, and elastic modulus of the flexible element and shell materials to provide satisfactory force-to-deflection characteristics of the resulting spring interconnection elements. Exemplary materials for the core element include gold. Exemplary materials for the coating include nickel and its alloys. The resulting spring interconnection element is suitably used to effect pressure, or demountable, interconnections between two or more electronic components, including semiconductor devices.

0013Commonly-owned, co-pending U.S. patent application Ser. No. 08/340,144, filed Nov. 15, 1994 and its corresponding PCT Patent Application No. PCT/US94/13373, filed Nov. 16, 1994 (WO95/14314, published May 16, 1995), both by Khandros and Mathieu, disclose a number of applications for the aforementioned spring interconnection elements, and also disclose techniques for fabricating tip structures at the ends of the interconnection elements. For example, a plurality of negative projections or holes, which may be in the form of inverted pyramids ending in apexes, are formed in the surface of a sacrificial layer (substrate). These holes are then filled with a contact structure comprising layers of material such as gold or rhodium and nickel. A flexible elongate element is mounted to the resulting tip structure and can be overcoated in the manner described hereinabove. In a final step, the sacrificial substrate is removed. The resulting spring interconnection element has a tip structure having controlled geometry (e.g., a sharp point) at its free end.

0014Commonly-owned, co-pending U.S. patent application Ser. No. 08/452,255, filed May 26, 1995 and its corresponding PCT Patent Application No. PCT/US95/14909, filed Nov. 13, 1995 (WO96/17278, published Jun. 6, 1996), both by Eldridge, Grube, Khandros and Mathieu, disclose additional techniques and metallurgies for fabricating tip structures on sacrificial substrates, as well as techniques for transferring a plurality of interconnection elements mounted thereto, en masse, to terminals of an electronic component.

0015Commonly-owned, co-pending U.S. patent application Ser. No. 08/788,740, filed Jan. 24, 1997 and its corresponding PCT Patent Application No. PCT/US96/08107, filed May 24, 1996 (WO96/37332, published Nov. 28, 1996), both by Eldridge, Khandros and Mathieu, disclose techniques whereby a plurality of tip structures are joined to a corresponding plurality of elongate interconnection elements that are already mounted to an electronic component. Also disclosed are techniques for fabricating “elongate” tip structures in the form of cantilevers. The cantilever tip structures can be tapered, between one end thereof and an opposite end thereof. The cantilever tip structures are suitable for mounting to already-existing (i.e., previously fabricated) raised interconnection elements extending (e.g., free-standing) from corresponding terminals of an electronic component.

0016Commonly-owned, co-pending U.S. patent application Ser. No. 08/819,464, filed Mar. 17, 1997, by Eldridge, Khandros and Mathieu, representatively discloses a technique whereby a plurality of elongate interconnection elements having different lengths than one another can be arranged so that their outer ends are disposed at a greater pitch than their inner ends. The inner, “contact” ends may be collinear with one another, for effecting connections to electronic components having terminals disposed along a line, such as a center line of the component.

0017As electronic components get increasingly smaller and the spacing between terminals on the electronic components get increasingly tighter or the pitch gets increasingly finer, it becomes increasingly more difficult to fabricate interconnections including spring interconnection elements suitable for making electrical connection to terminals of an electronic component. Co-pending and commonly-owned U.S. patent application Ser. No. 08/802,054, titled “Microelectronic Contact Structure, and Method of Making Same,” discloses a method of making spring interconnection elements through lithographic techniques. In one embodiment, that application discloses forming a spring interconnection element (including a spring interconnection element that is a cantilever beam) on a sacrificial substrate and then transferring and mounting the interconnection element to a terminal on an electronic component. In that disclosure, the spring interconnection element is formed in the substrate itself through etching techniques. In co-pending, commonly-owned U.S. patent application Ser. No. 08/852,152, titled “Microelectronic Spring Contact Elements,” spring interconnection elements are formed on a substrate, including a substrate that is an electronic component, by depositing and patterning a plurality of masking layers to form an opening corresponding to a shape embodied for the spring interconnection element, depositing conductive material in the opening made by the patterned masking layers, and removing the masking layer to form the free-standing spring interconnection element.

0018Co-pending and commonly-owned U.S. patent application Ser. No. 09/023,859, titled “Microelectronic Contact Structures and Methods of Making Same,” describes an interconnection element having a base end portion (post component), a body portion (beam component) and a contact end portion (tip component) and methods separately forming each portion and joining the post portion together as desired on an electronic component.

0019Co-pending and commonly-owned U.S. patent application Ser. No. 09/107,924 and its parent, U.S. Pat. No. 5,772,451 issued Jun. 30, 1998, both entitled “Sockets for Electronic Components and Methods of Connecting to Electronic Components,” show a socketing device for mating to a packaged semiconductor.

0020What is needed is a method of fabricating interconnection elements suitable for present fine-pitch electrical connections that is scalable for future technologies. Also needed are improved methods of making interconnection elements, particularly methods that are repeatable, consistent, and inexpensive.

SUMMARY OF THE INVENTION

0021An interconnection element is disclosed. In one embodiment, the interconnection element comprises a spring (body) comprising a first resilient element with a first contact region and a second contact region and a first securing region, and a second resilient element with a third contact region and a second securing region. The second resilient element is coupled to the first resilient element through respective securing regions. The second resilient element is positioned such that upon sufficient displacement of the first contact region toward the second resilient element, the second contact region will contact the third contact region.

0022The interconnection element of the invention is suitable for making either temporary or permanent electrical connection between terminals of an electronic component such as a PCB and a semiconductor chip. For making temporary connection, the electronic component interconnection element of the invention may be coupled to a substrate such as an electronic component and the electronic component may be brought together with another electronic component so that the one end of the interconnection element is in pressure contact with contact pad or a terminal of the other electronic component. The interconnection element reacts resiliently to maintain contact pressure and an electrical connection between the two components. For making a permanent connection, the electronic component upon which the interconnection element is coupled may be brought together with another electronic component and an attachment element of the interconnection element is joined or bonded, such as by soldering, welding, or brazing or with a conductive adhesive, to a terminal of the other electronic component. In one embodiment, the interconnection element is compliant and may accommodate differential thermal expansion between the two electronic components.

0023By fabricating a body of the interconnection element with a plurality of resilient elements, the mechanical properties of the interconnection element are improved over single beam spring interconnection elements, particularly in fine pitch spacing ranges of current and future technologies of contacts or terminals of an integrated circuit. This is useful for mating to a packaged semiconductor as in a socket for an LGA or BGA packaged device. This also is useful for mating directly to a semiconductor as in a chip-scale packaging application. In addition, this is useful for other chip-scale contacts such as probing a semiconductor device on a wafer. For example, the multiple resilient element (e.g., multiple-leaf) body of the interconnection element of the invention offers improved mechanical properties such as a higher spring constant, improved compliance, and lower material stress over similarly sized single beam spring interconnection elements in sub-micron applications.

0024An electronic component is also disclosed. In one aspect, the electronic component comprises a plurality of interconnection elements, coupled to a substrate and configured in a relation to contact an array of contact pads of a chip-scale device, each interconnection element comprising a first resilient element and second resilient element. The first resilient element includes a first and second contact region and a securing region. The second resilient element includes a third contact region and is coupled to the first resilient element through respective securing regions. The second resilient element is positioned such that upon sufficient displacement of the first contact region towards the second resilient element, the second contact region will contact the third contact region. The plurality of interconnection elements are arranged, for example, in an array to accommodate the connection or coupling of the interconnection elements with, for example, corresponding contact pads or terminals of a second electronic component.

0025An electronic component according to the invention is particularly suitable for making temporary or permanent electrical connection with a second electronic component having “fine-pitch” contact pads or terminals, for example, spacing of at least less than 5 mils (130 μm), such as 2.5 mils (65 μm). As will be evident from the description that follows, minimized pitch between interconnection elements of an electronic component of the invention is achieved in part by modifying the thickness of the body or spring portion of the interconnection element of the electronic component. Instead of a single beam body, the interconnection elements of the electronic component are comprised of a plurality of resilient elements to improve the mechanical properties of each interconnection element. A desired spring constant of multiple, coordinated springs reinforce and support the primary spring and interconnection element (e.g., tip). A leaf portion body also improves the compliance of the body at a reduced material stress. Applications to larger scale devices, including, for example, devices with contact pitches of about 50-100 mil (1.3-2.6 mm) and even larger are feasible as well.

0026Other embodiments, features, and advantages of the invention will become apparent in light of the following description thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

0027The features, aspects, and advantages of the invention will become more thoroughly apparent from the following detailed description, appended claims, and accompanying drawings in which:

0028<figref idref="DRAWINGS">FIG. 1</figref> is a cross-sectional side view of an example of an interconnection element having a single beam spring coupled to an electronic component.

0029<figref idref="DRAWINGS">FIG. 2</figref> shows the interconnection element of <figref idref="DRAWINGS">FIG. 1</figref> in contact with a second electronic component.

0030<figref idref="DRAWINGS">FIG. 3</figref> is a cross-sectional side view of an example of an interconnection element having a spring of multiple leaf portions coupled to an electronic component.

0031<figref idref="DRAWINGS">FIG. 4</figref> shows the interconnection element of <figref idref="DRAWINGS">FIG. 3</figref> in contact with a second electronic component.

0032<figref idref="DRAWINGS">FIG. 5</figref> is a graphical representation of the force applied to a single-beam interconnection element and a leaf-portioned interconnection element, respectively, versus deflection distance of the interconnection element.

0033<figref idref="DRAWINGS">FIG. 6</figref> shows the material stress for a single-beamed interconnection element and a leaf-portioned interconnection element, respectively, versus deflection distance of the interconnection element.

0034<figref idref="DRAWINGS">FIG. 7</figref> is a cross-sectional side view of a structure having a triangularly-shaped feature formed in a surface of a substrate with conductive layers overlying a surface of the substrate and the triangularly-shaped feature in accordance with an embodiment of forming an interconnection element of the invention on a sacrificial substrate.

0035<figref idref="DRAWINGS">FIG. 8</figref> shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after depositing a first masking material layer over a surface of the substrate and exposing the triangularly-shaped feature through an opening in the first masking material layer.

0036<figref idref="DRAWINGS">FIG. 9</figref> shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after depositing a first tip material in the opening in the first masking material layer.

0037<figref idref="DRAWINGS">FIG. 10</figref> shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after depositing a second tip material in the opening in the first masking material layer.

0038<figref idref="DRAWINGS">FIG. 11</figref> shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after planarizing the first masking material layer and the second tip material.

0039<figref idref="DRAWINGS">FIG. 12(</figref><i>a</i>) shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after removing the first masking material layer in accordance with one aspect of an embodiment of the invention.

0040<figref idref="DRAWINGS">FIG. 12(</figref><i>b</i>) shows the tip portion of <figref idref="DRAWINGS">FIG. 12(</figref><i>a</i>) after affixing the fabricated tip structure to a spring of a separately fabricated interconnection element in accordance with one aspect of an embodiment of the invention.

0041<figref idref="DRAWINGS">FIG. 13(</figref><i>a</i>) shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after depositing an adhesion/seed material over a portion of the planarized surface in accordance with a second aspect of an embodiment of the invention.

0042<figref idref="DRAWINGS">FIG. 13(</figref><i>b</i>) shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after patterning a second masking material layer over the substrate having an opening aligned to the tip, the opening extending laterally and/or transversely over the substrate from the tip in accordance with a second aspect of an embodiment of the invention.

0043<figref idref="DRAWINGS">FIG. 13(</figref><i>c</i>) shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after depositing a second conductive material in the opening of the second masking material layer in accordance with a second aspect of an embodiment of the invention.

0044<figref idref="DRAWINGS">FIG. 13(</figref><i>d</i>) shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after planarizing the second masking material and the second conductive material in accordance with a second aspect of an embodiment of the invention.

0045<figref idref="DRAWINGS">FIG. 14(</figref><i>a</i>) shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after removing the masking material layers to form an interconnection element including a spring having a single leaf portion and a tip structure in accordance with a third aspect of an embodiment of the invention.

0046<figref idref="DRAWINGS">FIG. 14(</figref><i>b</i>) shows the structure of <figref idref="DRAWINGS">FIG. 14(</figref><i>a</i>) after affixing the tip structure and spring to a separately fabricated post and spring (in this example consisting of one leaf portion) in accordance with a third aspect of an embodiment of the invention.

0047<figref idref="DRAWINGS">FIG. 14(</figref><i>c</i>) shows the structure of <figref idref="DRAWINGS">FIG. 14(</figref><i>b</i>) after separating the tip structure from its substrate to form a free-standing interconnection element on a substrate in accordance with a third aspect of an embodiment of the invention.

0048<figref idref="DRAWINGS">FIG. 15(</figref><i>a</i>) shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after depositing a third masking material layer over a portion of the planarized surface in accordance with a fourth aspect of an embodiment of the invention.

0049<figref idref="DRAWINGS">FIG. 15(</figref><i>b</i>) shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after depositing a seed material over a portion of the substrate in accordance with a fourth aspect of an embodiment of the invention.

0050<figref idref="DRAWINGS">FIG. 15(</figref><i>c</i>) shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after depositing a fourth masking material layer over a portion of the substrate defining an opening over the second conductive material in accordance with a fourth aspect of an embodiment of the invention.

0051<figref idref="DRAWINGS">FIG. 15(</figref><i>d</i>) shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after depositing a third conductive material in the opening of the fourth masking material layer in accordance with a fourth aspect of an embodiment of the invention.

0052<figref idref="DRAWINGS">FIG. 15(</figref><i>e</i>) shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after planarizing the third masking material layer and the third conductive material in accordance with a fourth aspect of an embodiment of the invention.

0053<figref idref="DRAWINGS">FIG. 15(</figref><i>f</i>) shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after depositing and patterning additional masking material layers, seed materials, and conductive materials to form two additional leaf portions in accordance with a fourth aspect of an embodiment of the invention.

0054<figref idref="DRAWINGS">FIG. 16(</figref><i>a</i>) shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after removing the masking material layers to form an interconnection element including a spring having four leaf portions and a tip structure in accordance with a fifth aspect of an embodiment of the invention.

0055<figref idref="DRAWINGS">FIG. 16(</figref><i>b</i>) shows the structure of <figref idref="DRAWINGS">FIG. 16(</figref><i>a</i>) after affixing the tip structure and spring to a separately fabricated post to form a free-standing interconnection element on a substrate in accordance with a fifth aspect of an embodiment of the invention.

0056<figref idref="DRAWINGS">FIG. 17(</figref><i>a</i>) shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after depositing a post masking material layer over the surface of the substrate and forming an opening to the seed material in accordance with a sixth aspect of an embodiment of the invention.

0057<figref idref="DRAWINGS">FIG. 17(</figref><i>b</i>) shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after depositing a post material in the opening to the seed material in accordance with a sixth aspect of an embodiment of the invention.

0058<figref idref="DRAWINGS">FIG. 17(</figref><i>c</i>) shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after planarizing the post masking material layer and the post material in accordance with a sixth aspect of an embodiment of the invention.

0059<figref idref="DRAWINGS">FIG. 17(</figref><i>d</i>) shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after removing the masking material layers in accordance with a sixth aspect of an embodiment of the invention.

0060<figref idref="DRAWINGS">FIG. 17(</figref><i>e</i>) shows the structure of <figref idref="DRAWINGS">FIG. 7</figref> after affixing the interconnection element formed in accordance with a sixth aspect of an embodiment of the invention to an electronic component.

0061<figref idref="DRAWINGS">FIG. 18</figref> shows a top view illustration of an application for an embodiment of the interconnection element of the invention wherein a plurality of interconnection elements are affixed to an electronic component and contact a plurality of contact pads or terminals arranged along the edge of a second electronic component.

0062<figref idref="DRAWINGS">FIG. 19</figref> shows a top view illustration of a second application for an embodiment of the interconnection element of the invention wherein a plurality of interconnection elements are affixed on an electronic component and contact a plurality of contact pads or terminals arranged in a row on a second electronic component.

0063<figref idref="DRAWINGS">FIG. 20(</figref><i>a</i>) shows a top view illustration of a first application for an embodiment of the interconnection element of the invention wherein a plurality of interconnection elements are affixed to an electronic component in a diagonal array and contact a plurality of contact pads or terminals on a second electronic component.

0064<figref idref="DRAWINGS">FIG. 20(</figref><i>b</i>) shows a top view illustration of a second application for an embodiment of the interconnection element of the invention wherein a plurality of interconnection elements are affixed to an electronic component in a diagonal array and contact a plurality of terminals on a second electronic component.

0065<figref idref="DRAWINGS">FIG. 21(</figref><i>a</i>) shows a top perspective view of a layout of adjacent interconnection elements fabricated with close spacing tolerances in accordance with an embodiment of the invention.

0066<figref idref="DRAWINGS">FIG. 21(</figref><i>b</i>) shows a cross-sectional view of the layout of interconnection elements of <figref idref="DRAWINGS">FIG. 21(</figref><i>a</i>) in accordance with an embodiment of the invention.

0067<figref idref="DRAWINGS">FIG. 21(</figref><i>c</i>) shows a top perspective view of a layout of adjacent interconnection elements fabricated with close spacing tolerances in accordance with another embodiment of the invention.

0068<figref idref="DRAWINGS">FIG. 21(</figref><i>d</i>) shows a cross-sectional view of the layout of interconnection elements of <figref idref="DRAWINGS">FIG. 21(</figref><i>c</i>) fabricated in accordance with an embodiment of the invention.

0069<figref idref="DRAWINGS">FIG. 21(</figref><i>e</i>) shows a top view illustration of a plurality of interconnection elements affixed to an electronic component in an overlayed fashion so that their tips align in accordance with an embodiment of the invention.

0070<figref idref="DRAWINGS">FIG. 21(</figref><i>f</i>) shows a top view illustration of a plurality of interconnection elements affixed to an electronic component in an overlayed fashion so that their tips are staggered in accordance with an embodiment of the invention.

0071<figref idref="DRAWINGS">FIG. 22(</figref><i>a</i>) shows a top view of a first exemplary layout of a leaf portion over a substrate in accordance with the invention.

0072<figref idref="DRAWINGS">FIG. 22(</figref><i>b</i>) shows a top view of a second exemplary layout of a leaf portion over a substrate in accordance with the invention.

0073<figref idref="DRAWINGS">FIG. 22(</figref><i>c</i>) shows a top view of a third exemplary layout of a leaf portion over a substrate in accordance with the invention.

0074<figref idref="DRAWINGS">FIG. 22(</figref><i>d</i>) shows a top view of a fourth exemplary layout of a leaf portion over a substrate in accordance with the invention.

0075<figref idref="DRAWINGS">FIG. 22(</figref><i>e</i>) shows a top view of a fifth exemplary layout of a leaf portion over a substrate in accordance with the invention.

0076<figref idref="DRAWINGS">FIG. 22(</figref><i>f</i>) shows a top view of a sixth exemplary layout of a leaf portion over a substrate in accordance with the invention.

0077<figref idref="DRAWINGS">FIG. 22(</figref><i>g</i>) shows a top view of a seventh exemplary layout of a leaf portion over the substrate in accordance with the invention.

0078<figref idref="DRAWINGS">FIG. 23(</figref><i>a</i>) shows a cross-sectional side view of a seventh exemplary layout of a leaf portion over a substrate in accordance with the invention.

0079<figref idref="DRAWINGS">FIG. 23(</figref><i>b</i>) shows a cross-sectional side view of an eighth exemplary layout of a leaf portion over a substrate in accordance with the invention.

0080<figref idref="DRAWINGS">FIG. 24(</figref><i>a</i>) shows an embodiment of an interconnection element of the invention having a plurality of leaf portions of different dimensions.

0081<figref idref="DRAWINGS">FIG. 24(</figref><i>b</i>) shows the interconnection element of <figref idref="DRAWINGS">FIG. 24(</figref><i>a</i>) subjected to a force at its tip.

0082<figref idref="DRAWINGS">FIG. 25(</figref><i>a</i>) shows an embodiment of an interconnection element of the invention having a plurality of leaf portions coupled to one another through non-aligned supports.

0083<figref idref="DRAWINGS">FIG. 25(</figref><i>b</i>) shows the interconnection element of <figref idref="DRAWINGS">FIG. 25(</figref><i>a</i>) subjected to a force at its contact region.

0084<figref idref="DRAWINGS">FIG. 26(</figref><i>a</i>) shows an embodiment of an interconnection element of the invention having a plurality of variable length leaf portions.

0085<figref idref="DRAWINGS">FIG. 26(</figref><i>b</i>) shows the interconnection element of <figref idref="DRAWINGS">FIG. 26(</figref><i>a</i>) subjected to a force at its contact region.

0086<figref idref="DRAWINGS">FIG. 27(</figref><i>a</i>) shows an embodiment of an interconnection element of the invention having a plurality of leaf portions coupled to one another at their proximal and distal ends.

0087<figref idref="DRAWINGS">FIG. 27(</figref><i>b</i>) shows the interconnection element of <figref idref="DRAWINGS">FIG. 27(</figref><i>a</i>) subjected to a force at its contact region.

0088<figref idref="DRAWINGS">FIG. 28(</figref><i>a</i>) shows an embodiment of an interconnection element of the invention having a plurality of leaf portions coupled to another by staggered supports and a contact region of a tip coupled to a surface of a superiorly-located leaf portion between its ends.

0089<figref idref="DRAWINGS">FIG. 28(</figref><i>b</i>) shows the interconnection element of <figref idref="DRAWINGS">FIG. 28(</figref><i>a</i>) subjected to a force at its contact region.

0090<figref idref="DRAWINGS">FIG. 29(</figref><i>a</i>) shows a side view of an embodiment of an interconnection element of the invention having a plurality of cylindrical leaf portions coupled to one another by staggered supports.

0091<figref idref="DRAWINGS">FIG. 29(</figref><i>b</i>) shows a second side view of the interconnection element of <figref idref="DRAWINGS">FIG. 29(</figref><i>a</i>).

0092<figref idref="DRAWINGS">FIG. 29(</figref><i>c</i>) shows a top perspective view of the interconnection element of <figref idref="DRAWINGS">FIG. 29(</figref><i>a</i>).

0093<figref idref="DRAWINGS">FIG. 29(</figref><i>d</i>) shows the interconnection element of <figref idref="DRAWINGS">FIG. 29(</figref><i>a</i>) subjected to a force at its contact region.

0094<figref idref="DRAWINGS">FIG. 30</figref> shows a top perspective view of an embodiment of a leaf portion of an interconnection element of the invention having a cylindrical shape with a “clover leaf”-shaped opening.

0095<figref idref="DRAWINGS">FIG. 31</figref> shows a top perspective view of an embodiment of a leaf portion of an interconnection element of the invention having a “H”-shape.

0096<figref idref="DRAWINGS">FIG. 32</figref> shows a top perspective view of an embodiment of a leaf portion of an interconnection element of the invention having a rectangular shape with a rectangularly-shaped opening.

0097<figref idref="DRAWINGS">FIG. 33(</figref><i>a</i>) shows a cross-sectional side view of a layout of adjacent interconnection elements collectively forming an apparatus suitable as a micro-switch.

0098<figref idref="DRAWINGS">FIG. 33(</figref><i>b</i>) shows a top perspective view of the layout of <figref idref="DRAWINGS">FIG. 33(</figref><i>a</i>).

0099<figref idref="DRAWINGS">FIG. 33(</figref><i>c</i>) shows a planar top view of the layout of <figref idref="DRAWINGS">FIG. 33(</figref><i>a</i>).

0100<figref idref="DRAWINGS">FIG. 34</figref> shows a second method of fabricating an interconnection element on a substrate and shows a substrate having a tip structure formed through a masking material layer.

0101<figref idref="DRAWINGS">FIG. 35</figref> shows the structure of <figref idref="DRAWINGS">FIG. 34</figref> after removing the masking material layer that defines the pattern for the tip structure.

0102<figref idref="DRAWINGS">FIG. 36</figref> shows the structure of <figref idref="DRAWINGS">FIG. 34</figref> after introducing a first conductive material mask layer over the substrate.

0103<figref idref="DRAWINGS">FIG. 37</figref> shows the structure of <figref idref="DRAWINGS">FIG. 34</figref> after planarizing the first conductive material mask layer and the tip structure.

0104<figref idref="DRAWINGS">FIG. 38</figref> shows the structure of <figref idref="DRAWINGS">FIG. 34</figref> after patterning a second masking material layer and introducing a first body material.

0105<figref idref="DRAWINGS">FIG. 39</figref> shows the structure of <figref idref="DRAWINGS">FIG. 34</figref> after removing the second masking material layer.

0106<figref idref="DRAWINGS">FIG. 40</figref> shows the structure of <figref idref="DRAWINGS">FIG. 34</figref> after introducing a second conductive material layer mask over the structure.

0107<figref idref="DRAWINGS">FIG. 41</figref> shows the structure of <figref idref="DRAWINGS">FIG. 34</figref> after planarizing the second conductive material layer mask and the first body material.

0108<figref idref="DRAWINGS">FIG. 42</figref> shows the structure of <figref idref="DRAWINGS">FIG. 34</figref> after introducing a third conductive material layer mask over the structure.

0109<figref idref="DRAWINGS">FIG. 43</figref> shows the structure of <figref idref="DRAWINGS">FIG. 34</figref> after patterning a third masking material layer over the structure.

0110<figref idref="DRAWINGS">FIG. 44</figref> shows the structure of <figref idref="DRAWINGS">FIG. 34</figref> after exposing the first body material through the patterning of second masking material layer.

0111<figref idref="DRAWINGS">FIG. 45</figref> shows the structure of <figref idref="DRAWINGS">FIG. 34</figref> after patterning a second masking material layer to define an opening for a second body material.

0112<figref idref="DRAWINGS">FIG. 46</figref> shows the structure of <figref idref="DRAWINGS">FIG. 34</figref> after introducing a second body material.

0113<figref idref="DRAWINGS">FIG. 47</figref> shows the structure of <figref idref="DRAWINGS">FIG. 34</figref> after removing the second masking material layer.

0114<figref idref="DRAWINGS">FIG. 48</figref> shows the structure of <figref idref="DRAWINGS">FIG. 34</figref> after introducing a fourth conductive material layer mask over the structure.

0115<figref idref="DRAWINGS">FIG. 49</figref> shows the structure of <figref idref="DRAWINGS">FIG. 34</figref> after planarizing the fourth conductive material layer mask and the second body material.

0116<figref idref="DRAWINGS">FIG. 50</figref> shows the structure of <figref idref="DRAWINGS">FIG. 34</figref> after forming a plurality of body material layers and a post structure.

0117<figref idref="DRAWINGS">FIG. 51</figref> shows the structure of <figref idref="DRAWINGS">FIG. 34</figref> after removing a plurality of conductive material layer masks.

0118<figref idref="DRAWINGS">FIG. 52</figref> shows the structure of <figref idref="DRAWINGS">FIG. 34</figref> after removing a seed layer to expose an underlying release layer of the substrate.

DETAILED DESCRIPTION OF THE INVENTION

0119The invention relates to interconnection elements, including contact elements. According to one aspect of the invention, the invention contemplates a method of forming an interconnection element having a body including a plurality of resilient or flexural elements, e.g., leaf portions. The invention also relates to a method of bringing together two substrates, such as an electronic component having a plurality of interconnection elements with a second electronic component having an array of contact pads or terminals.

0120Suitable electronic components include, but are not limited to, an active semiconductor device, a memory chip, a portion of a semiconductor wafer, a ceramic substrate, an organic substrate, a PCB, an organic membrane, a polyimide sheet, a space transformer, a probe card, a chip carrier, and a socket. The electronic component may be an active device or a passive device that supports one or more electronic connections. In general, suitable electronic components include, but are not limited to, devices comprising an integrated circuit having at least two contacts or terminals providing electrical access to the circuit. Such a device is representatively demonstrated by an integrated circuit chip (or microchip) having a plurality of exposed contacts or terminals providing access to the integrated circuit of the device.

0121The interconnection element or elements of the invention may be fabricated on or independent of the electronic component to which it is or they are joined. In the case of independent fabrication, the invention contemplates that the interconnection element or elements can be fabricated with a shape, size, and metallurgy that are not limited by the materials and layout considerations associated with the manufacture of the electronic component. Independent fabrication also avoids the exposure of the electronic component to the process conditions associated with forming the interconnection element.

0122Disposed on an electronic component such as a space transformer of a probe card assembly, the interconnection elements of the invention are designed to accommodate contact pads or terminals of electronic components having very small pitch or spacing tolerances. In one embodiment, the interconnection elements adopt alternating orientation (e.g., left-right-left-right) so as to achieve a greater pitch between their post portion than at the tip portion. In another embodiment, the interconnection elements adopt alternating lengths (e.g., short-long-short-long) so as to achieve a greater pitch between the post portion than at the tip portion of adjacent interconnection elements. Similarly, alternating interconnection elements can be fabricated to have a greater pitch at their tip portions than their post portions. In summary, the interconnection elements, whether fabricated on or independent of the electronic component to which they are joined may adopt a variety of orientations to accommodate various configurations associated with the electronic components which they connect.

0123<figref idref="DRAWINGS">FIG. 1</figref> and <figref idref="DRAWINGS">FIG. 2</figref> illustrate one embodiment of a spring interconnection element. Methods of formation of such a spring interconnection element are described in detail in application Ser. No. 09/205,023 entitled “Lithographic Contact Elements.” <figref idref="DRAWINGS">FIG. 1</figref> shows interconnection element <b>10</b> comprising post <b>13</b>, beam or body <b>14</b>, and tip structure <b>16</b>. Post <b>13</b> is disposed on terminal <b>11</b> of electronic component <b>9</b>. Post <b>13</b> has a height, h₂. Body <b>14</b> is coupled at one end to post <b>13</b>. For consistency, in the discussion that follows the end of an elongate beam body that is coupled to the post will be referred to as the proximal end. Of course, one of skill in the art will recognize that when discussing a body structure that is a beam or a plurality of beams or leaf portions, elements need not be positioned at ends of the beam.

0124In one embodiment shown in <figref idref="DRAWINGS">FIG. 1</figref>, body <b>14</b> is a single beam having a thickness equivalent to a height, t₁, and length, l_B. At the other end of body <b>14</b> (e.g., the distal end) and coupled to a side opposite post <b>13</b> is contact or tip structure <b>16</b>. Tip structure <b>16</b> has a height, h₁, from the surface of body <b>14</b>.

0125<figref idref="DRAWINGS">FIG. 2</figref> shows interconnection element <b>10</b> under load such as when accommodating a substrate under test. In this case, substrate <b>20</b> having terminal <b>21</b> is brought into contact with interconnection element <b>10</b> and an inferiorly-directed (e.g., downward) force, F, is applied at tip structure <b>16</b> of interconnection element <b>10</b> to deflect interconnection element <b>10</b> at its distal end towards electronic component <b>9</b>. <figref idref="DRAWINGS">FIG. 2</figref> shows deflected interconnection element <b>10</b> separated from electronic component <b>9</b> at its distal end by a height, h₃.

0126Under load, such as when contacting substrate <b>20</b>, body <b>14</b> of interconnection element <b>10</b> deflects by an amount represented in <figref idref="DRAWINGS">FIG. 2</figref> by δ. A spring constant, k, may be calculated for this deflection as follows: <br /><i>k=F/δ. </i><br /> Controlling the spring constant for each interconnection element of an electronic component, such as in a probe card assembly, allows a consistent contact force to be applied to each terminal, such as terminal <b>21</b> of a substrate under test (such as substrate <b>20</b>). Hundreds to thousands of interconnection elements may be utilized in a probing operation and many tens of thousands in a wafer-scale contactor. Thus, consistent spring force is particularly significant.

0127Decreasing device sizes allows a corresponding increase in contact or terminal density. In order for interconnection elements on a second electronic component to accommodate the increased array density by a corresponding interconnection element array on the second electronic component, the interconnection element array must correspondingly become more dense. One way to increase the density of an interconnection element array on an electronic component is to reduce the size of the individual interconnection elements. Thus, an interconnection element, such as interconnection element <b>10</b> of <figref idref="DRAWINGS">FIG. 1</figref>, may be reduced in its length, l_B, and its width (not shown) to permit a greater density (e.g., smaller pitch) array on an electronic component (e.g., increase the number of interconnection elements that occupy a given space).

0128Reduction in the length and width of a particular interconnection element (e.g., reduction in the surface area of the interconnection element) affects the mechanical properties of the interconnection element. For example, the spring constant of a resilient interconnection element, k, is directly related to the geometry (e.g., length, width, and thickness) of the interconnection element. Thus, reduction in thickness for a given length and width beam, correspondingly reduces the spring constant of the interconnection element (k ∝ thickness³). A reduction of the spring constant generally reduces the amount of load or force that may be applied to interconnection elements for a given deflection. Similarly, a reduction in the width of an interconnection element for a given length and thickness, correspondingly reduces the spring constant of the interconnection element (k ∝ width), as does a reduction in length for a given width and thickness (k ∝ length⁻³).

0129In certain situations, it may be desirous to reduce the size of an interconnection element without reducing the amount of load or force desired to be applied to the interconnection element. In order to accommodate an acceptable force, for example, on an interconnection element having a substantially rectangular beam in a high density interconnection element array, the thickness of the body of an interconnection element may be increased. In <figref idref="DRAWINGS">FIG. 1</figref>, for example, the thickness of body <b>14</b>, t₁, may be increased to account for a decreased length, l_B, and width. However, increasing the thickness of the body generally increases the stress of the body. Increasing the stress of a body decreases the longevity or number of compression cycles to failure of the interconnection element.

0130The stress of a particular body material is generally a measurement of the deformation of the material under a force or load. In general, a material may withstand a certain amount of stress in which the deformation is reversible. Beyond this point, the deformation reversibility decreases to a point of “permanent set” corresponding to the yield stress of the material. The yield stress is material dependent. In general, in spring applications such as representatively described for the interconnection element of the invention, the maximum stress on an interconnection element material is designed to be less than about one-half the 0.2 percent offset yield stress of the material for maximum longevity of operation.

0131The interconnection element of the invention addresses an objective of increasing the density of interconnection elements on an electronic component by adjusting the thickness of each interconnection element, assuming that the length and width are set to a predetermined maximum permitted by the geometry. In this manner, an increase in the density of interconnection elements on an electronic component may be achieved without a corresponding reduction in spring constant or a reduction in the acceptable load or force applied to the interconnection elements. The increased thickness of the portion of the interconnection element of the invention may also be achieved without a reduction in the allowable maximum stress on the material.

0132<figref idref="DRAWINGS">FIG. 3</figref> and <figref idref="DRAWINGS">FIG. 4</figref> illustrate one embodiment of an interconnection element of the invention. <figref idref="DRAWINGS">FIG. 3</figref> shows interconnection element <b>30</b> comprising post <b>33</b>, body <b>34</b>, and contact or tip structure <b>36</b>. Post <b>33</b> is disposed as a first attachment element on terminal <b>11</b> of electronic component <b>9</b>. Post <b>33</b> has a height, h₂, over substrate <b>9</b>. Body <b>34</b> is coupled at one end of post <b>33</b>. Body <b>34</b> includes a plurality (in this case, four) flexural elements or leaf portions <b>35</b> each having a thickness or height, t₂, that collectively define a width (not shown), a thickness or height, t₃and length, l_B. The superiorly-located leaf portion <b>35</b> defines a superior surface for body <b>34</b> to which tip structure <b>36</b>, as a second attachment element, is coupled. Tip structure <b>36</b> has a height, h₁, from the superior surface of spring <b>34</b>. In this embodiment, tip structure <b>36</b> is coupled to body <b>14</b> at an end opposite post <b>13</b>. Again, it is to be appreciated that this configuration is only illustrative.

0133<figref idref="DRAWINGS">FIG. 4</figref> shows interconnection element <b>30</b> under load such as when accommodating a substrate under test. In this case, substrate <b>20</b> having terminal <b>21</b> is brought into contact with interconnection element <b>30</b> through an inferiorly-directed force, F, applied at tip structure <b>36</b> of interconnection element <b>30</b> to deflect interconnection element <b>30</b>. The deflection, δ₂, of interconnection element <b>30</b> causes tip structure <b>36</b> to “wipe” contact pad or terminal <b>21</b> in a lateral direction as the interconnection element deflects. This wiping action serves, in one sense, to improve the connection between tip structure <b>36</b> and contact pad or terminal <b>21</b> by cutting through debris or build-up on the contact or terminal.

0134In one embodiment, the height of the post, h₂, is greater than the height of the tip structure, h₁, so that post <b>33</b> determines the over-travel or deflection distance of body <b>34</b>. A suitable over-travel or deflection distance according to current technologies is 2-8 mils (50-200 microns). As shown in <figref idref="DRAWINGS">FIG. 4</figref>, electronic component <b>20</b> “bottoms-out” on the superior surface of body <b>34</b>. In this configuration, the superior surface of body <b>34</b> may be coated with an insulative layer to limit possible errant currents.

0135Other alternatives for limiting the over-travel or deflection distance of the interconnection element of the invention are also suitable. For example, the height of tip structure, h₁, can be greater than the height of the post, h₂. In this situation, electronic component <b>20</b> will not bottom-out on the superior surface of body <b>34</b>. To protect the distal end of the inferiorly-located leaf portion of body <b>34</b> from contacting the surface of electronic component <b>9</b>, travel stop <b>37</b> (indicated in dotted lines) may be added. Alternatively, post stop <b>38</b> (also indicated in dotted lines) may be fabricated to a predetermined height adjacent interconnection element <b>30</b> to limit the superiorly-directed advancement of electronic component <b>20</b>. Alternative travel stop <b>37</b> and post stop <b>38</b>, respectively, are, in one aspect, comprised of an insulating material.

0136<figref idref="DRAWINGS">FIG. 5</figref> and <figref idref="DRAWINGS">FIG. 6</figref> graphically compare the force and stress of a single beam body and a leaf portion body interconnection element according to the invention. <figref idref="DRAWINGS">FIG. 5</figref> shows that the amount of force to deflect a body is greater for a single beam structure having a thickness t₁such as shown in <figref idref="DRAWINGS">FIG. 1</figref> as compared to a single leaf portion having a thickness t₂shown, for example, in <figref idref="DRAWINGS">FIG. 3</figref> provided the thicknesses are set as shown.

0137<figref idref="DRAWINGS">FIG. 6</figref> shows a graphical representation of the stress of a material for a single beam body and a leaf portion of, for example, a multiple-leaf body of an interconnection element according to the invention. <figref idref="DRAWINGS">FIG. 6</figref> shows that for a given deflection distance, corresponding, for example, to a contact force shown in <figref idref="DRAWINGS">FIG. 5</figref>, the stress on a body material, σ, is greater for a single beam of thickness, t₁, than a leaf portion of thickness, t₂, of a multiple-leaf body. In order to remain below the maximum stress, σ_max, the deflection distance of the single beam body must be limited. Increasing the thickness of the single beam further limits the deflection distance even more.

0138In general, in the example of an interconnection element having a rectangular body or spring such as shown in <figref idref="DRAWINGS">FIG. 1</figref> (single beam) and <figref idref="DRAWINGS">FIG. 3</figref> (multiple leaf), the spring constant of an interconnection element is directly related to the thickness of the interconnection element. Thus, reducing the thickness of a body portion of an interconnection element reduces the spring constant (k_leaf&lt;k_beam) which correspondingly reduces the contact force required to deflect the interconnection element a predetermined distance. In order to achieve a desired spring constant of, for example, the spring constant of the beam, k_beam, multiple (n) leaf portions each having a thickness, t₂, are combined such that n·k_leaf≈k_beam. It is to be appreciated that the spring constant of an interconnection element, including a multiple leaf interconnection element described in the invention will vary with the application (e.g., the length of the beam spring, interconnection material, the desired deflection distance, etc.).

0139As shown in <figref idref="DRAWINGS">FIG. 6</figref>, the stress on a single leaf portion of, for example, a multiple-leaf body (the multiple-leaf body collectively having a similar material thickness to a single beam) is much less for a given deflection distance (e.g., a given amount of force) as compared to the single beam body. Accordingly, a single leaf portion may have a much greater compliance and be subjected to a much greater deflection than a single beam body of equivalent spring constant and remain below the maximum stress of the material. Thus, in designing an interconnection element according to the invention, the thickness of each leaf portion, t₂(see <figref idref="DRAWINGS">FIG. 3</figref>) may be determined to be below the maximum stress and the number of leaf portions may be selected to achieve a desired spring constant.

0140The following example compares a single beam body (spring) interconnection element such as interconnection element <b>10</b> with a leaf-portioned body (spring) interconnection element such as interconnection element <b>30</b>. In this example, each interconnection element is limited to a body length, l_B, of 10 mils (250 μm) and a maximum stress, σ_MAX, of 1×10⁵pounds per square inch (psi) or 7000 kilograms-force per square centimeter (kg/cm²). The body of each interconnection element is comprised of a nickel-cobalt (NiCo) alloy with a Young's modulus of 30×10⁶psi (2.1×10⁶kg/cm²).

0141In the case of a single beam body having a thickness, t₁, of 0.001 inches (25.4 μm) and a constant width of 0.0055 inches (139.7 μm), the maximum spring deflection is 2.2×10⁻⁴inches (5.6 μm) and the force is 4.1 gram-force (gmf). The spring constant is 18.7 gmf/mil (0.74 gmf/μm).

0142In the case of a two-leaf structure with equivalent spring rate, the spring constant for each leaf portion (k_1/2) is approximately 9.3 gmf/mil (0.36 gmf/μm) for a thickness, t₂, of 0.00079 inches (2.0 μm). Such a configuration allows a deflection distance of 2.8×10⁻⁴inches (7.1 μm) to develop 100 ksi stress. By combining two leaf portions, a spring constant of 18.6 gmf/mil (0.73 gmf/μm) is produced, approximately the spring constant of the single beam described above. The multi-leaf body, however, is capable of a deflection of 2.8×10⁻⁴inches (7.1 μm) as compared to 2.2×10⁻⁴inches (5.6 μm) for the single beam body, an improvement of 127 percent in allowed deflection. For a three leaf-portioned body, the improvement in allowed deflection is 145 percent; for a four leaf-portioned body, 162 percent.

0143It is to be appreciated that the above example representatively compares a single beam interconnection element with a multiple leaf portion interconnection element. Accordingly, the dimensions of the interconnection element bodies and values of spring constant and deflection distance are similarly representative and not intended to confine the invention. For example, multiple leaf structures having individual spring constants on the order of 0.05 to 0.3 gmf/mil (0.002 to 0.02 gmf/μm) or greater are useful in interconnection elements employing multiple leaf portions (e.g., two or more) according to current state of the art applications.

0144As contact pad or terminal densities on electronic components increase, the area of corresponding interconnection elements of a corresponding electronic component configured to connect to or probe the contact pads or terminals will be reduced. Thus, for example, the length and width of individual interconnection elements on an electronic component will be determined by the array of the corresponding contact pad or terminal array of the electronic component to be contacted. The invention offers the ability to achieve a desired spring constant, contact force, and deflection distance and meet the increased contact pad or terminal density requirements of current and future technologies.

0000A. Fabrication of a Multi-Leaf or Multi-Tier Spring Interconnect Element

0145<figref idref="DRAWINGS">FIGS. 7-17(</figref><i>e</i>) illustrate one method of making an interconnection element in accordance with one embodiment of the invention. In one aspect, an interconnection element that is a cantilever including a post, a body comprising a plurality of leaf portions, and a tip structure will be fabricated in this embodiment. It is to be appreciated that at a given time, a number of interconnection elements can be formed on a substrate. The method described below focuses on the formation of a single interconnection element. The discussion, however, applies also to the fabrication of a number of interconnection elements on a substrate, such as a sacrificial substrate or an electronic component, at a given time. Typically, each of the interconnection elements fabricated on a substrate will have substantially similar characteristics (e.g., dimensions, shape, etc.). It is also appreciated, however, that the characteristics of the interconnection elements of a substrate can be individually controlled and determined for given application requirements.

0146<figref idref="DRAWINGS">FIG. 7</figref> shows structure <b>100</b> including substrate <b>110</b> that is a sacrificial substrate such as, for example, a semiconductor (e.g., silicon) substrate. For illustration purposes, substrate <b>110</b> is oriented to show a finished interconnection element. The orientation during manufacturing may be quite different. The method of making an interconnection element will be described according to current processing methodologies including device scale. It is to be appreciated that the principles of the invention may be adapted to future methodologies and that the techniques described are scalable.

0147Formed in a surface of substrate <b>110</b> is a pyramidally-shaped feature. Methods for forming a pyramidally-shaped feature are described in detail in commonly-owned pending PCT Application No. PCT/US97/08606, published Nov. 20, 1997 as WO97/43653. In PCT Application No. PCT/US97/08606, a method is described whereby a pyramidally-shaped feature is formed by the patterning of a masking material having a preferably square opening measuring, according to current technologies, approximately 1-4 mils (25-100 μm) on a side over a semiconductor substrate. Next, the substrate is etched to form the pyramidally-shaped depression. In the case of certain silicon semiconductor substrates, silicon will tend to be self-limiting as the etching proceeds along the crystal plane, such as at approximately 54.74° for silicon. In other words, the depression will extend to a depth that is dictated by the size of the mask opening and the nature of the substrate. For example, with square openings of 2.5 mils (63.5 μm) per side, the depth of the depression will be approximately 2 mils (50.8 μm) in wafer-grade silicon.

0148Other methods of forming pyramidally-shaped features are described in commonly-owned U.S. Pat. No. 5,809,128 and co-pending and commonly-owned U.S. patent application Ser. No. 08/802,054, titled “Microelectronic Contact Structure, and Method of Making Same.”

0149Overlying the surface of substrate <b>110</b> is release layer <b>125</b>. Release layer <b>125</b> is, for example, a metal such as aluminum or titanium-tungsten, deposited to a thickness of approximately 5000 angstroms (Å) using conventional deposition techniques. Overlying release layer <b>125</b> on the surface of substrate <b>110</b> is seed layer <b>130</b>. Seed layer <b>130</b> is, for example, copper, palladium, or titanium-tungsten that facilitates a further deposition technique such as an electroplating process such as by establishing an appropriate potential for an electrolytic process. In one embodiment, seed layer <b>130</b> of titanium-tungsten is introduced over the surface of substrate <b>110</b> to a thickness of approximately 5000 Å using conventional (e.g., sputter) deposition techniques. Alternatively, a bilayer of two materials may be introduced as seed layer <b>130</b>. In one embodiment, a layer of gold or palladium is introduced at a thickness of, for example, a few thousand angstroms followed by the introduction of a second material such as titanium-tungsten. Seed layer <b>130</b> may be introduced as a blanket layer over substrate <b>110</b> or as multiple, non-contiguous regions.

0150<figref idref="DRAWINGS">FIG. 8</figref> shows structure <b>100</b> after the introduction and patterning of first masking material layer <b>135</b> over substrate <b>110</b>. First masking material layer <b>135</b> is, for example, a photopolymer (e.g., a positive or negative photoresist) that is spin-coated onto the surface of substrate <b>110</b> to a thickness of the desired height of a tip structure of an interconnection element taking into consideration the possibility of planarizing a portion of first masking material layer <b>135</b> with tip structure material. Approximately 1-4 mils (25-100 μm) is a useful height range for many applications. First masking material layer <b>135</b> is patterned to have an opening over feature <b>120</b>.

0151Next, as shown in <figref idref="DRAWINGS">FIG. 9</figref>, first tip material <b>137</b> is introduced in the opening in first masking material layer <b>135</b>. Suitable materials for first tip material <b>137</b> include, but are not limited to, palladium (Pd), gold (Au), and rhodium (Rh) and their alloys, including nickel (Ni) and cobalt (Co) alloys. First tip material <b>137</b> is introduced, in one example, to a thickness of about 1 to 5 μm but more can be used—even tens of microns or more. Suitable introduction techniques include, but are not limited to, electroplating, chemical vapor deposition, sputter deposition, and electroless plating. In this example, first tip material <b>137</b> serves as an outer contact layer in the finished product.

0152<figref idref="DRAWINGS">FIG. 10</figref> shows a process of forming an interconnection element according to an embodiment of the invention where second tip material <b>140</b> is introduced to a suitable thickness. This may be at least the height of first masking material layer <b>135</b> (the height of opening <b>120</b>) or greater than such height. Suitable introduction techniques include, but are not limited to, electroplating, chemical vapor deposition, sputter deposition, and electroless plating. In one embodiment, second tip material <b>140</b> is an alloy of nickel and cobalt (NiCo) introduced by an electroplating process to a height greater than the height of first masking material layer <b>135</b> (i.e., overplating). A suitable total height is about 1-4 mils (25.4-101.6 μm), particularly about 3 mils (76.2 μm).

0153<figref idref="DRAWINGS">FIG. 11</figref> shows structure <b>100</b> after planarizing second tip material <b>140</b> and first masking layer <b>135</b> in accordance with an embodiment of the invention. The planarization is accomplished, for example, by a mechanical polish or a chemical-mechanical polish with a suitable slurry. Suitable mechanical polishes include diamond-based materials and silicon carbide. Suitable slurries for a chemical-mechanical polish of the materials described above include silicon dioxide, aluminum oxide, and cesium oxide in a pH-adjusted slurry. The planarization described in <figref idref="DRAWINGS">FIG. 11</figref> defines the height of the tip structure of an interconnection element.

0154In a first aspect of an embodiment of the invention, the tip structure of first tip material <b>137</b> and second tip material <b>140</b> may be removed and separately affixed to an interconnection element, such as for example, an interconnection element containing a post and a body formed on an electronic component. <figref idref="DRAWINGS">FIG. 12(</figref><i>a</i>) shows structure <b>100</b> after removing first masking material layer <b>135</b>. In the example where first masking material layer <b>135</b> is a photoresist, first masking material layer <b>135</b> may be removed by an etch (e.g., oxygen ashing), reactive ion etching, laser ablation, or wet etching. The removal of first masking material layer <b>135</b> may also remove seed layer <b>130</b>. Alternatively, an additional procedure (e.g., etch) may be performed to remove seed layer <b>130</b> and expose release layer <b>125</b>. Once first masking material layer <b>135</b> and seed layer <b>140</b> are removed, the tip structure of first tip material <b>137</b> and second tip material <b>140</b> may be separated from substrate <b>110</b> at release layer <b>125</b>. In the example where release layer <b>125</b> is aluminum, the tip structure may be removed from substrate <b>110</b> by dissolving release layer <b>125</b> using a sodium hydroxide (NaOH) solution as known in the art. Other methods of separation including but not limited to chemical etching and heat are also suitable, as known in the art. In the example where seed layer <b>130</b> is a bilayer of gold followed by titanium-tungsten, a portion of seed layer <b>130</b> that may remain on the tip structure may serve as appropriate contact material.

0155Before the tip structure is separated from substrate <b>110</b>, the tip structure may be combined with a post and a body as shown in <figref idref="DRAWINGS">FIG. 12(</figref><i>b</i>) by, for example, brazing, soldering, or welding. <figref idref="DRAWINGS">FIG. 12(</figref><i>b</i>) shows an example of interconnection element <b>1500</b> coupled to electronic component <b>1000</b>. Interconnection element <b>1500</b> includes post <b>1650</b>, coupled to terminal <b>1010</b> of electronic component <b>1000</b> and body <b>1550</b>. Body <b>1550</b> includes multiple (e.g., four shown) cantilever leaf portions. A method of forming the leaf portions of a body will be discussed below with respect to a further aspect of an embodiment of the invention. For present purposes, <figref idref="DRAWINGS">FIG. 12(</figref><i>b</i>) shows the tip structure of first tip material <b>137</b> and second tip material <b>140</b> secured to a superior surface of body <b>1550</b> at an end opposite post <b>1650</b> in this example.

0156<figref idref="DRAWINGS">FIG. 13(</figref><i>a</i>) shows a second aspect of an embodiment of the invention. Starting from structure <b>100</b> as shown in <figref idref="DRAWINGS">FIG. 11</figref>, <figref idref="DRAWINGS">FIG. 13(</figref><i>a</i>) shows structure <b>100</b> after rendering a portion of first masking material layer <b>135</b> conductive to define an electrode area for a body of the interconnection element that is to be formed by an electroplating process. In one embodiment, a portion of an area over first masking material layer <b>135</b> is covered with a thin adhesion/seed layer. Typical adhesion materials include, but are not limited to, titanium, tungsten, molybdenum, chrome, and copper, alone or as an alloy. Typical seed materials include, but are not limited to, gold, copper, silver, platinum and palladium. Another example of an adhesion/seed layer is an adhesion layer of palladium-tin chloride and a seed layer of electroless palladium. Seed layer <b>145</b> may be introduced via a blanket deposition, such as a sputter deposition. For an electroplated nickel-cobalt layer, for example, a seed layer having a thickness according to current technologies of about between 1500 to 6000 Å, may be suitably introduced by, for example, a blanket sputter deposition process over the surface of first masking material <b>135</b>. Alternatively, seed layer <b>145</b> may be introduced as a plurality of “traces,” each trace corresponding to an area over a first masking material layer <b>135</b> where the body of the interconnection element is to be formed to serve, in one manner, as an electroform whereupon the body can be fabricated.

0157In yet another embodiment, a stencil (shadow mask) may be introduced over the surface of first masking material layer <b>135</b>. A stencil may be used, for example, to introduce a discontinuous adhesion/seed layer. The stencil typically will have a plurality of openings extending laterally from an area above the corresponding tip structure (indicated by first tip material <b>137</b> and second tip material <b>140</b>) to define areas for the body of the interconnection elements. The stencil may suitably be a thin (e.g., about 2 mils (50.8 μm) thick for current technologies) foil of stainless steel, tungsten, or molybdenum that may be punched or etched to have openings. The stencil can be any suitable material having any suitable thickness that will permit seed layer <b>145</b> to be deposited onto first masking material layer <b>135</b> in a pattern of conductive traces corresponding to the shape of the opening in the stencil. With the stencil in place (typically, slightly above the surface of substrate <b>110</b>), seed layer <b>145</b> is deposited, such as by sputtering, onto the exposed surface of first masking layer <b>135</b>. The stencil may then be removed.

0158Consideration should be given, in certain instances, to the selection of the material for the masking material layer and the process for deposition of the seed layer. In general, the masking material should be stable in the environment of the deposition method. Compatibility considerations are within the level of ordinary skill in the art.

0159Next, as shown in <figref idref="DRAWINGS">FIG. 13(</figref><i>b</i>), an area over substrate <b>110</b> is covered by second masking material layer <b>150</b>, again such as a photopolymer (e.g., photoresist) bearing in mind the consideration of using multiple masking materials in the presence of conductive layers, including seed layers. Second masking material layer <b>150</b> is patterned to define opening <b>151</b> over structure <b>100</b>.

0160Second masking material layer <b>150</b> defines an area over structure <b>100</b> for a first leaf portion (e.g., a cantilever leaf portion) of a body in accordance with one embodiment of the invention. The area corresponding to opening <b>151</b> in second masking material layer <b>150</b> will be determined, in this embodiment, based, in part, on the desired area for the leaf. The desired area of opening <b>151</b> will depend, to a large extent in one embodiment, on the density and disposition (distribution) of a contact pad or terminal array that an electronic component of a plurality of interconnection elements will be probing or contacting. For example, for an electronic component having a pitch of approximately 6 mils (152 μm) or less between contacts or terminals, the length and width of an interconnection element in an array must be sized so that it can contact one contact pad or terminal and allow, for example, an adjacent interconnection element of the array to contact an adjacent contact pad or terminal. One way this is achieved is shown by the illustration shown in <figref idref="DRAWINGS">FIG. 20(</figref><i>a</i>) and <figref idref="DRAWINGS">FIG. 20(</figref><i>b</i>). In <figref idref="DRAWINGS">FIG. 20(</figref><i>a</i>), for example, contacts or terminals <b>710</b> are disposed on an electronic component having a pitch of, for example, 6 mils (152 μm). Interconnection elements <b>715</b> are disposed diagonally on electronic component <b>720</b> (shown in dashed lines). Interconnection elements <b>725</b> are cantilever interconnection elements having a rectangular body of a plurality of leaf portions (not shown in <figref idref="DRAWINGS">FIG. 20(</figref><i>a</i>)). Each interconnection element has a length of approximately 12 mils (304.8 μm) and a width of 3 mils (76.2 μm) or a total area of 24 mil²(2.3×10⁴μm²). Such an area will correspond, in one embodiment, to the area of each leaf portion of a cantilever spring of an interconnection element such as illustrated in the process of <figref idref="DRAWINGS">FIGS. 7-17(</figref><i>e</i>).

0161The thickness of second masking material layer <b>150</b> will determine in part the thickness of a leaf portion of the body of the interconnection element formed by the process in this embodiment. Thus, second masking material layer <b>150</b> is introduced to a desired thickness of a leaf portion of a body of the interconnection element bearing in mind a subsequent planarization step. A suitable thickness of a leaf portion will be determined based in part on considerations of the desired spring constant, the deflection distance of the body, and the stress property of the material chosen for the leaf portion of a body. In one embodiment, for a nickel-cobalt body (having a Young's modulus of 30×10⁶psi (2.1×10⁶kg/cm²) and maximum stress, σ_mof 1×10⁵psi (7000 kg/cm²), a leaf portion having a length of 21 mils (533 μm) and a thickness of about 0.5 mil (12.7 μm) will support about 1 mil (25.4 μm) of compliance.

0162<figref idref="DRAWINGS">FIG. 13(</figref><i>c</i>) shows structure <b>100</b> after introducing first body material <b>155</b> over the surface of substrate <b>110</b>. In one embodiment, first body material <b>155</b> is conductive material introduced by an electroplating process with an electroplate alloy such as nickel-cobalt. In <figref idref="DRAWINGS">FIG. 13(</figref><i>c</i>), first body material <b>155</b> is introduced to a thickness greater than the thickness of second masking material layer <b>150</b>. As noted, it is to be appreciated that the amount introduced and the thickness of first body material <b>155</b> will depend, in part, on the desired thickness of the particular leaf portion of the body.

0163As shown in <figref idref="DRAWINGS">FIG. 13(</figref><i>d</i>), after the introduction of first body material <b>155</b> over substrate <b>110</b>, first body material <b>155</b> and second masking material <b>150</b> are planarized by way of, for example, a grinding process or a chemical-mechanical polish such as described above to form a leaf portion of the interconnection element on substrate <b>110</b>. Planarization of first body material <b>155</b> and second masking material <b>150</b> controls the final thickness of the leaf portion of the body (i.e., controls the thickness of first body material <b>155</b>) thus allowing a determinable and consistent leaf portion to be fabricated.

0164In a third aspect of an embodiment of the invention, the tip structure of first tip material <b>137</b> and second tip material <b>140</b> and a leaf portion of first body material <b>155</b> may be removed and separately affixed to an interconnection element, such as for example, an interconnection element containing a post and, optionally, a body of one or more leaf portions formed on an electronic component. <figref idref="DRAWINGS">FIG. 14(</figref><i>a</i>) shows structure <b>100</b> after the further processing step of removing first masking material layer <b>135</b> and second masking material layer <b>150</b>. In the example where first masking material layer <b>135</b> and second masking material layer <b>150</b> is a photoresist, the layers may be removed by an etch (e.g., oxygen ashing), reactive ion etching, laser ablation, or wet etching. Once the masking material layers are removed, the tip structure and leaf portion body may be removed from substrate <b>110</b> by, for example, dissolving release layer <b>125</b> using a sodium hydroxide (NaOH) solution as known in the art.

0165Before the tip structure and leaf portion body are separated from substrate <b>110</b>, the leaf portion may be combined with a post and, optionally, one or more leaf portions as shown in <figref idref="DRAWINGS">FIG. 14(</figref><i>b</i>) by, for example, brazing, soldering, or welding. <figref idref="DRAWINGS">FIG. 14(</figref><i>b</i>) shows an example of interconnection element <b>1550</b> coupled to electronic component <b>1580</b>. Interconnection element <b>1550</b> includes post <b>1572</b> and leaf portion <b>1575</b>. The affixing of the leaf portion of first body material <b>155</b> to leaf portion <b>1575</b> provides a spacer between the leaf portions. The amount of connecting material can be varied to adjust this spacing. <figref idref="DRAWINGS">FIG. 14(</figref><i>c</i>) shows a free-standing interconnection element after the separation of substrate <b>110</b> from the tip structure.

0166<figref idref="DRAWINGS">FIG. 15(</figref><i>a</i>) shows a fourth aspect of an embodiment of the invention. Starting from structure <b>100</b> as shown in <figref idref="DRAWINGS">FIG. 13(</figref><i>d</i>), <figref idref="DRAWINGS">FIG. 15(</figref><i>a</i>) shows depositing of third masking material layer <b>158</b> over a surface of structure <b>100</b>. In this embodiment, third masking material layer <b>158</b> is, for example, a photoresist similar to the previous masking material layers. Third masking material layer <b>158</b> may also be a metal layer (e.g., copper), conductive polymer, or other layer preferred for later removal by etching (wet or dry) or solvent removal. The thickness of third masking material layer <b>158</b> defines, in part, the thickness of a gap between adjacent leaf portions of a spring of the interconnection element. Third masking material layer <b>158</b> also defines a portion of first body material <b>155</b> to which a subsequent leaf portion of a body of the interconnection element may be coupled. Stated alternatively, third masking material layer <b>158</b> serves, in this embodiment, to provide an area less than the entire surface area of first body material <b>155</b> to connect a second leaf portion and inhibit the plating together of adjacent leaf portions. Opening <b>159</b> provides access to first body material <b>155</b> to allow plating to a portion of first body material <b>155</b>.

0167In one embodiment, third masking material layer <b>158</b> is a layer of photoresist similar to the previous masking material layers. Third masking material layer <b>158</b> may be, for example, on the order of 0.1 to 5 μm.

0168In the discussion that follows, the masking material layers, including third masking material layer <b>158</b> will be removed leaving a free standing inverted interconnection element on substrate <b>110</b> and an air gap between adjacent leaf portions of the body of the interconnection element. As an alternative to introducing a removable masking material layer to be removed to form an air gap between adjacent leaf portions, a thin layer of an “interleaf” material may be introduced that inhibits the complete plating of adjacent leaf portions and will not inhibit the deflection of individual leaf portions. Suitable interleaf material includes, but is not limited to, TEFLON® polymers (commercially available from E.I. duPont de Nemours &amp; Co. of Wilmington, Del.) diamond, brass, or a PARALENE® polymer (commercially available from E.I. duPont de Nemours). Opening <b>159</b> is patterned with the interleaf material to first body material <b>155</b> to allow plating of a subsequent leaf portion to the leaf portion that is first body material <b>155</b>.

0169<figref idref="DRAWINGS">FIG. 15(</figref><i>b</i>) shows the introduction of another adhesion/seed layer. Adhesion/seed layer <b>160</b> may be, in one embodiment, similar to adhesion/seed layer <b>145</b> and may be introduced via a blanket deposition. For an electroplated nickel-cobalt, for example, an adhesion/seed layer of gold or copper having a thickness of 3000-5000 Å may be suitably introduced over the surface of third masking material layer <b>158</b>.

0170As shown in <figref idref="DRAWINGS">FIG. 15(</figref><i>c</i>), an area of structure <b>100</b> is covered with fourth masking material layer <b>161</b>, again such as a photoresist similar to the previous masking material layers bearing in mind considerations of using multiple masking material layers in the presence of conductive layers. Fourth masking material layer <b>161</b> is patterned to define opening <b>162</b> that defines an area for a second leaf portion of the body of the interconnection element. In one embodiment, the patterning of fourth masking material layer <b>161</b> defines an area (e.g., a length and width for a cantilever leaf portion) similar to second masking material layer <b>150</b>. The considerations of the thickness of fourth masking material layer <b>161</b> are similar to the considerations discussed above with reference to second masking material layer <b>150</b>. In other embodiments, leaf portions of a spring may have different areas. Leaf portions may be dissimilar not only in length (as illustrated in <figref idref="DRAWINGS">FIGS. 24(</figref><i>a</i>) and <b>24</b>(<i>b</i>)), but even profile. The configuration of the individual leaf portions can be selected by the designer for optimal performance in a particular environment. The invention provides a mechanism for individually configuring leaf portions to suit a designer's needs.

0171Next, as shown in <figref idref="DRAWINGS">FIG. 15(</figref><i>d</i>), second body material <b>163</b> is introduced over substrate <b>110</b>. In one embodiment, second body material is a conductive material introduced through an electroplating process with an electroplated alloy such as nickel-cobalt. Second body material <b>163</b> is introduced to a thickness greater than the thickness of fourth masking material layer <b>161</b> of a second leaf portion of the body of the interconnection element.

0172As shown in <figref idref="DRAWINGS">FIG. 15(</figref><i>e</i>), after the introduction of second body material <b>163</b> over substrate <b>110</b>, second body material <b>163</b> and fourth masking material layer <b>161</b> are planarized by way of, for example, a grinding process or a chemical-mechanical polish to form a second leaf portion of a body of the interconnection element. As noted above, in the case of a cantilever leaf portion of a body, the thickness will depend to a large extent on the desired spring constant, the deflection distance, and the material stress. In one embodiment, the thickness of second body material <b>163</b> will be similar to the thickness of first body material <b>155</b>. In other embodiments, such as those illustrated below, leaf portions of a body may have different thicknesses and different profiles to modify the properties of the interconnection element.

0173The above-described process and patterning of masking material layers, introducing a seed layer, introducing a conductive material, and planarizing a masking material layer and the body material may be repeated numerous times to form additional leaf portions of a body of an interconnection element. The number of leaf portions will depend, primarily, on the desired spring constant for a predetermined deflection distance and material stress for the material of the interconnection element of the invention. <figref idref="DRAWINGS">FIG. 15(</figref><i>f</i>) shows structure <b>100</b> after the subsequent introduction, patterning, and planarizing steps of forming two additional leaf portions of a body of the interconnection element. In total, an interconnection element shown in <figref idref="DRAWINGS">FIG. 15(</figref><i>f</i>) has a body of four leaf portions.

0174<figref idref="DRAWINGS">FIG. 16(</figref><i>a</i>) and <figref idref="DRAWINGS">FIG. 16(</figref><i>b</i>) show a fifth aspect of one embodiment of the invention. In this aspect, the fabrication of the component for the interconnection element formed by the lithographic techniques described is substantially complete with the formation of a spring interconnection element having a tip structure of first tip portion <b>137</b> and second tip portion <b>140</b> and a body of multiple (e.g., four) leaf portions denoted principally by body material <b>155</b>, <b>163</b>, <b>166</b>, and <b>170</b>. <figref idref="DRAWINGS">FIG. 16(</figref><i>a</i>) shows structure <b>100</b> after removing the masking material layers (e.g., masking material layers <b>135</b>, <b>150</b>, <b>158</b>, <b>161</b>, <b>164</b>, <b>167</b>, <b>168</b>, and <b>169</b>). In the example where each of the masking material layers are a photoresist, the step of removing the masking material layers may be accomplished with an etch (e.g., oxygen ashing), reactive ion etching, laser ablation, or wet etching. An additional etch may be required to remove excess or undesired portions of the various seed layers. However, because the seed layers are typically thin (e.g., about 5000 Å according to current technologies), any excess or undesired seed layer material is typically removed with the removal of the masking material layer(s). In this manner, <figref idref="DRAWINGS">FIG. 16(</figref><i>a</i>) shows an interconnection element affixed at its tip to substrate <b>110</b> and a body of four laterally and/or transversely extending leaf portions.

0175The sacrificial substrate of <figref idref="DRAWINGS">FIG. 16(</figref><i>a</i>) including a tip structure and body of an interconnection element may be affixed to a separately-fabricated post to form an interconnection element on an electronic component as shown in <figref idref="DRAWINGS">FIG. 16(</figref><i>b</i>). In this manner, sacrificial substrate <b>110</b> is aligned with post <b>1650</b> so that the inferiorly located leaf portion of the body (relative to the tip structure) may be affixed to post portion <b>1650</b> at a proximal end of the leaf portion (an end opposite the tip structure end of the leaf portion) to create a cantilever body as shown in <figref idref="DRAWINGS">FIG. 16(</figref><i>b</i>). The body may be affixed to post <b>1650</b> by, for example, soldering, welding, or brazing. Separately fabricated post <b>1650</b> is coupled to electronic component <b>1010</b> at a contact pad or terminal of electronic component <b>1010</b>. Post <b>1650</b> may be formed directly on an electronic component or transferred from a sacrificial substrate.

0176Once the body of the interconnection element is affixed to post <b>1650</b>, the tip structure is separated from sacrificial substrate <b>110</b> at release layer <b>125</b>. In the example where release layer <b>125</b> is aluminum, one method of separating the tip from sacrificial substrate <b>110</b> is by reacting release layer <b>125</b> with a sodium hydroxide (NaOH) solution. <figref idref="DRAWINGS">FIG. 16(</figref><i>b</i>) shows the final interconnection element coupled to electronic component <b>1010</b>. Any remaining unwanted seed material <b>130</b> adjacent first tip material <b>137</b> may be removed with a subsequent etch or retained as contact material.

0177Instead of separating the interconnection element containing a tip structure and a body from sacrificial substrate <b>110</b>, a sixth aspect of an embodiment of the invention contemplates the forming of a post for the interconnection element on the sacrificial substrate. <figref idref="DRAWINGS">FIGS. 17(</figref><i>a</i>)-<b>17</b>(<i>e</i>) illustrate this process.

0178<figref idref="DRAWINGS">FIG. 17(</figref><i>a</i>) shows structure <b>100</b> of <figref idref="DRAWINGS">FIG. 15(</figref><i>f</i>) after the patterning of post masking material layer <b>199</b> over structure <b>100</b> including an opening to the inferiorly located leaf portion (leaf portion defined by conductive material <b>170</b>) at the proximal end of conductive material <b>170</b> (i.e., proximal relative to the location of the tip structure of the interconnection element on the end of the leaf portion defined principally by reference numeral <b>155</b>). Post masking material <b>199</b> is, for example, photoresist material similar to other masking material layers. Prior to patterning post masking material layer <b>199</b>, an adhesion/seed layer may be patterned over leaf portion <b>170</b> similar, in one embodiment, to adhesion/seed layer <b>145</b> described above. As noted above, the described adhesion/seed layers facilitate, in one aspect, an electrolytic process of introducing interconnection material. It is to be appreciated that such adhesion/seed layers may not be necessary, particularly where the masking material that is used to fabricate the interconnection element is conductive material. One example of such a process is described with reference to <figref idref="DRAWINGS">FIGS. 34-52</figref> and the accompanying text.

0179Post masking material layer <b>199</b> is, for example, photoresist material similar to other masking material layers (e.g., first masking material layer <b>135</b>, second masking material layer <b>150</b>, third masking material layer <b>158</b>, fourth masking material layer <b>161</b>, fifth masking material layer <b>164</b>, sixth masking material layer <b>167</b>, seventh masking material layer <b>168</b>, and eighth masking material layer <b>171</b>). Post masking material layer <b>199</b> is patterned to a suitable height for a post of an interconnection element including consideration for a subsequent planarization step to define the height of the post. The thickness of post masking material layer <b>199</b> will primarily determine the distance that the main body portion (i.e., spring and tip) of the interconnection element is spaced away from the surface of an electronic component. In an example where resiliency is desired, the dimension of the post, the body, and the tip structure may be coordinated to maximize the contact force of the tip structure with, for example, a terminal of an electronic component, and minimize the potential “bottoming out” of the deflected body. For current technologies according to the method described, a suitable height of post masking material <b>199</b> is approximately 1-30 mils (25-750 μm), and preferably 3-8 mils (75-200 μm).

0180<figref idref="DRAWINGS">FIG. 17(</figref><i>b</i>) shows structure <b>100</b> after introducing post material <b>205</b> in the opening and post masking material layer <b>199</b> via, for example, an electroplating process. In one example, post material <b>205</b> is nickel-cobalt similar to the body of the interconnection element (e.g., first body material <b>155</b>, second body material <b>163</b>, third body material <b>166</b>, and fourth body material <b>170</b>). Post material <b>205</b> is preferably introduced to a thickness of at least the thickness of post masking material layer <b>199</b>, and generally greater than the thickness of post masking material layer <b>199</b> (e.g., overplating).

0181<figref idref="DRAWINGS">FIG. 17(</figref><i>c</i>) shows structure <b>100</b> after planarizing post material <b>205</b> and post masking material layer <b>199</b> to define a desired thickness for the post of the interconnection element. The planarization may be accomplished in a manner similar to the planarization procedures described above.

0182<figref idref="DRAWINGS">FIG. 17(</figref><i>d</i>) shows structure <b>100</b> after removing the masking material layers. In the example where the various masking material layers (e.g., first masking material layer <b>135</b>, second masking material <b>150</b>, third masking material layer <b>158</b>, fourth masking material layer <b>161</b>, fifth masking material layer <b>165</b>, sixth masking material layer <b>167</b>, seventh masking material layer <b>168</b>, eighth masking material layer <b>171</b> and post masking material layer <b>199</b> illustrated together in <figref idref="DRAWINGS">FIG. 17(</figref><i>c</i>)) are photoresist, an oxygen ashing, reactive ion etching, laser ablation or wet chemical etch step may be used to remove the masking material layers. The removal of the masking material layers leaves the interconnection element affixed at its tip structure to sacrificial substrate <b>110</b> as shown in <figref idref="DRAWINGS">FIG. 17(</figref><i>d</i>).

0183One technique for mounting the interconnection element shown in <figref idref="DRAWINGS">FIG. 17(</figref><i>d</i>) to an electronic component is by retaining the interconnection element on the sacrificial substrate as shown in <figref idref="DRAWINGS">FIG. 17(</figref><i>d</i>) and aligning post <b>205</b> with a corresponding terminal on an electronic component, whereupon post <b>205</b> may be suitably soldered, brazed, welded, etc., to a contact pad or terminal. It is to be appreciated that any suitable technique and/or material for affixing the post of the interconnection element to a contact pad or terminal of an electronic component may be employed. Once the interconnection element is affixed to an electronic component, sacrificial substrate <b>110</b> may be removed in a suitable manner, such as the dissolution of release layer <b>125</b> by sodium hydroxide (NaOH), chemical etching, heating, etc. Any remaining unwanted seed material layer <b>130</b> adjacent first tip material <b>130</b> may be removed with a subsequent etch or retained as contact material.

0184<figref idref="DRAWINGS">FIG. 17(</figref><i>e</i>) shows the interconnection element having tip structure <b>201</b> of first tip portion <b>137</b> and second tip portion <b>140</b>, body <b>200</b>, and post <b>205</b> coupled to contact pad or terminal <b>212</b> of electronic component <b>210</b>. Electronic component <b>210</b> is, for example, a space transformer of a probe card assembly or another integrated circuit. Electronic component <b>210</b> is, for example, a semiconductor- or ceramic-based substrate having contact pads or terminals on opposing surfaces. In the case of a commercially available ceramic-based electronic component <b>210</b>, for example, the electronic component includes terminals <b>212</b> and <b>215</b> on opposing surfaces of the electronic component. Terminals <b>212</b> and <b>215</b> are connected, for example, to conductive circuits <b>216</b> running through the electronic component such as, for example, a molybdenum or tungsten or molybdenum/tungsten circuit. Terminals <b>212</b> and <b>215</b> on electronic component <b>210</b> are, for example, copper, nickel, and gold terminals that may be suitable for connecting to an interconnection element by, for example, soldering. In one example, the copper facilitates the electroplating process and is the upper layer. The nickel acts a barrier between the gold and the copper.

0185<figref idref="DRAWINGS">FIG. 17(</figref><i>e</i>) shows an interconnection element having body <b>200</b> of four leaf portions. Adjacent leaf portions are coupled to one another at their proximal ends to form a cantilever spring. The area at which the leaf portions are coupled is represented by supports <b>202</b>. In the embodiment described supports <b>202</b> comprise a portion of adhesion/seed layer and a portion of body material selected to comprise a sufficient thickness to resist bending forces and maintain structural integrity. Spacing is provided by gaps <b>201</b> where masking material was originally deposited, as described above. It is to be appreciated that, according to this embodiment, supports <b>202</b> may be fabricated as discrete structures apart from the fabrication of a subsequent leaf portion such as, for example, by introducing and seeding an opening of a masking material and depositing a conductive material for supports <b>202</b>. Planarization of the masking material and the conductive material may also be desirous. The thickness of supports <b>202</b> may also be varied.

0186As is evident in <figref idref="DRAWINGS">FIG. 17(</figref><i>e</i>) (and <figref idref="DRAWINGS">FIGS. 14(</figref><i>c</i>) and <b>16</b>(<i>b</i>)), a plurality of elongate or cantilever interconnection elements such as described can be affixed to an electronic component having a plurality of contacts or terminals on the surface thereof. In this embodiment, each interconnection element has a post, a body, and a tip structure opposite the post. Each interconnection element is affixed at its post to a corresponding contact pad or terminal of an electronic component. The tip structure of each interconnection element extends above the surface of the electronic component to a position that is laterally and/or transversely offset from the post forming a free standing, cantilever structure. When affixed to an electronic component, the interconnection element of the invention has a height of “L<b>2</b>,” this being the distance between the highest portion of the tip structure and the inward-most portion where the post is affixed to electronic component <b>210</b>. A representative height, L<b>2</b>, for an interconnection element according to current technologies is, for example, 10-20 mils and will depend, in part, on considerations of contact pad or terminal spacing on an electronic component to be contacted or probed by an array of interconnection elements, deflection distance of the interconnection element, and the spring constant of the interconnection element.

0187In <figref idref="DRAWINGS">FIG. 17(</figref><i>e</i>), the distance between the underside of the inferiorly-located leaf portion of body <b>200</b> and the surface of electronic component <b>210</b> represents the distance that the interconnection element can deflect (absent any stops) in response to a compressive force applied at the tip structure. The height of post <b>205</b> and contact pad or terminal <b>212</b> (and any bonding material thickness) primarily determines this distance. A similar relationship applies between the superiorly-located leaf portion of body <b>200</b> and the end of tip <b>201</b>. Reference is made to <figref idref="DRAWINGS">FIG. 4</figref> and the accompanying text that describe the travel of the interconnection element.

0188The above embodiments described an interconnection element coupled to a substrate that is or is part of an electronic component and the interconnection element serves as a conductive path from a contact pad or terminal. It is to be appreciated that the interconnection element of the invention need not be coupled to a contact pad or terminal and need not serve as a conductive path. Instead, an interconnection element that is, for example, a mechanical spring is also contemplated.

0189The lithographic technique of forming an interconnection element on a sacrificial substrate is representative of one technique of forming the interconnection elements of the invention. A second technique where the interconnection element is formed directly on an electronic component is also contemplated. Reference is made to patent application Ser. No. 09/205,022 filed Dec. 2, 1998 entitled “Lithographic Contact Elements,” and patent application Ser. No. 09/205,023 filed Dec. 2, 1998 entitled “Lithographic Contact Elements,” co-owned by the assignee of the invention described herein, which describe such a technique and which are incorporated by reference. It is to be appreciated that the techniques described herein of forming interconnection elements having a body with a plurality of leaf portions can be incorporated into the discussions of forming interconnection elements on an electronic component described in these other applications.

0000B. Exemplary Applications of Spring Interconnect Structures

0190<figref idref="DRAWINGS">FIG. 18</figref> illustrates an application wherein a plurality of interconnection elements <b>500</b> such as those described hereinabove are arranged on a substrate such as a space transformer of a probe card assembly and affixed thereto in the manner described hereinabove, so that their tip structure ends are disposed in a manner suitable for making contact with the bond pad of a semiconductor device having its contact pads or terminals arranged along its periphery. This application is similar to the application described in co-pending, commonly-owned U.S. patent application Ser. No. 08/802,054, titled “Microelectronic Contact Structure, and Method of Making Same.” In <figref idref="DRAWINGS">FIG. 18</figref>, each interconnection element <b>500</b> includes post <b>502</b> (denoted by “x”) and tip structure <b>504</b> and is mounted to an electronic component such as a space transformer (schematically illustrated by the dashed line <b>510</b>) of a probe card assembly. Tip structures <b>504</b> are arranged in a pattern, mirroring the pattern of contact pads or terminals <b>522</b> (illustrated schematically by circles) of an electronic component (schematically illustrated by dashed line <b>520</b>) such as a semiconductor device. Interconnection elements <b>500</b> “fan-out” from their tip structures <b>504</b>, so that each of their posts <b>502</b> is disposed at a greater pitch (spacing from one another) than their tip structures <b>504</b>.

0191<figref idref="DRAWINGS">FIG. 19</figref> illustrates another application (also similarly described in co-pending, commonly-owned U.S. patent application Ser. No. 08/802,054) wherein a plurality of interconnection elements <b>600</b> such as those described hereinabove are arranged on a substrate such as a space transformer of a probe card assembly and affixed thereto in the manner described hereinabove, so that their tip structures are disposed in a manner suitable for making contact with the contact pads or terminals of a semiconductor device having its contact pads or terminals arranged in a row along a center line thereof. In <figref idref="DRAWINGS">FIG. 19</figref>, each interconnection element, generally denoted by reference numeral <b>600</b>, includes post <b>602</b> (denoted by “x”) and tip structure <b>604</b>, and are mounted to an electronic component such as a space transformer of a probe card assembly (schematically illustrated by dashed line <b>610</b>). Tip structures <b>604</b> are arranged, in a pattern mirroring that of contact pads or terminals <b>622</b> (illustrated schematically by circles) of an electronic component (schematically illustrated by dashed line <b>620</b>) such as a semiconductor device. In this example, the pitch of contact pads or terminals <b>622</b> in an xy-direction is 2 mils (50.8 μm) by 1.414 mils (35.9 μm), respectively. Interconnection elements <b>600</b> are arranged in the following sequence. First interconnection element <b>600</b><i>a </i>is relatively short (e.g., has the length in an x-direction of, in this embodiment, approximately 60 mils (1524 μm)), and is disposed to extend towards one side (right, as used) of electronic component <b>620</b>. Second interconnection element <b>600</b><i>b </i>is adjacent first interconnection element <b>600</b><i>a </i>and is also relatively short (e.g., a length in an x-direction of, in this embodiment, approximately 60 mils (1524 μm)), and is disposed to extend towards an opposite side (left, as used) of electronic component <b>620</b>. Third interconnection element <b>600</b><i>c </i>is adjacent second interconnection element <b>600</b><i>b </i>and is relatively long (e.g., has a length in an x-direction of, in this embodiment, approximately 80 mils (2032 μm)), and is disposed to extend towards the one side (right, as used) of electronic component <b>620</b>. Finally, fourth interconnection element <b>600</b><i>d </i>is adjacent third interconnection element <b>600</b><i>c </i>and is also relatively long (e.g., has a length in an x-direction of, in this embodiment, approximately 80 mils (2032 μm)), and is disposed to extend towards the opposite side (left, as used) of electronic component <b>620</b>. In this manner, tip structures <b>604</b> are disposed at a fine pitch commensurate with that of contact pads or terminals <b>622</b>, and posts <b>602</b> are disposed at a significantly greater pitch from one another.

0192<figref idref="DRAWINGS">FIG. 20(</figref><i>a</i>) shows a third application wherein a plurality of interconnection elements <b>715</b> such as those described hereinabove are arranged on a substrate such as electronic component <b>720</b> (shown in dashed lines) and affixed thereto in the manner described hereinabove, to accommodate the contacting of a densely packed array of contact pads or terminals <b>710</b> on electronic component <b>700</b>. In this embodiment, interconnection elements <b>715</b> are arranged in a diagonal array in an x-y plane over contact pads or terminals <b>710</b> to accommodate a pitch between contact pads or terminals <b>710</b> that is not suitable for a longitudinally or laterally extending array of interconnection elements. Interconnection elements <b>715</b> are arranged over contact pads or terminals <b>710</b> such that the tip structures of interconnection elements <b>715</b> contact the contact pads or terminals <b>710</b>. Posts <b>725</b> are located at the proximal end of the rectangular body of interconnection elements <b>715</b>. As illustrated in <figref idref="DRAWINGS">FIG. 20(</figref><i>a</i>), in one embodiment, interconnection elements <b>715</b> are arranged in a non-aligned relation relative to their contacting of contact pads or terminals <b>710</b> in the same row of electronic component <b>700</b>.

0193<figref idref="DRAWINGS">FIG. 20(</figref><i>b</i>) illustrates an application wherein a plurality of interconnection elements <b>716</b> such as those described hereinabove are arranged on a substrate such as electronic component <b>721</b> (shown in dashed lines) and affixed thereto in the manner described hereinabove, to accommodate the contacting of a densely packed array (3 across) of contact pads or terminals <b>711</b> on electronic component <b>701</b>. As illustrated in <figref idref="DRAWINGS">FIG. 20(</figref><i>b</i>), in one embodiment, interconnection elements <b>716</b> are arranged in an aligned relation relative to their contacting of contact pads or terminals <b>711</b> in the same row of electronic component <b>701</b>.

0194<figref idref="DRAWINGS">FIG. 20(</figref><i>a</i>) and <figref idref="DRAWINGS">FIG. 20(</figref><i>b</i>) illustrate that the length (“l”) and width (“w”) of an individual interconnection element may be limited by the spacing of contact pads or terminals <b>710</b>. To maintain the desired spring constant, deflection distance, and a material stress less than the maximum stress, interconnection elements <b>715</b> or <b>716</b> must be increased in the z-direction (coming out of page of <figref idref="DRAWINGS">FIG. 20(</figref><i>a</i>) and <figref idref="DRAWINGS">FIG. 20(</figref><i>b</i>)). The multiple leaf portion body of the interconnection element of the invention accommodates this requirement.

0000C. Exemplary Layouts of Spring Interconnect Structures

0195By using photolithographic techniques as described above, the interconnection elements according to the invention may be fabricated with an area array pitch corresponding to the reduced pitch of state-of-the-art electronic components. Accordingly, the interconnection elements according to the invention are well-suited to the fine-pitch, close-tolerance environment of micro-electronic components. <figref idref="DRAWINGS">FIGS. 21(</figref><i>a</i>)-<b>21</b>(<i>b</i>) illustrate one layout where pitch between adjacent interconnection elements may be further minimized. <figref idref="DRAWINGS">FIGS. 21(</figref><i>a</i>) and <b>21</b>(<i>b</i>) show two different views of adjacent interconnection elements <b>740</b>A and <b>740</b>B. Adjacent interconnection elements <b>740</b>A and <b>740</b>B may be fabricated directly on an electronic component or on a sacrificial substrate and transferred to an electronic component similar to the process steps above with respect to <figref idref="DRAWINGS">FIGS. 7-17(</figref><i>e</i>) and the accompanying text. In this embodiment, adjacent interconnection elements are stacked at slight angles to separate the tip structures. As interconnection elements are depressed, the body of the adjacent interconnection elements do not contact each other, at least in one embodiment.

0196Interconnection element <b>740</b>A includes post <b>730</b>A, body <b>745</b>A and tip structure <b>760</b>A. Interconnection element <b>740</b>B includes post <b>730</b>B, body <b>745</b>B and tip structure <b>760</b>B. As a further enhancement, interconnection element <b>740</b>B includes spacers <b>732</b>B and <b>733</b>B to align interconnection element <b>740</b>B at a similar height (in a z-direction) as interconnection element <b>740</b>A. Interconnection element <b>740</b>A also includes spacers <b>731</b>A and <b>732</b>A to separate, in this example, body <b>745</b>A of interconnection element <b>740</b>A from underlying interconnection element <b>740</b>B. In the manner where interconnection elements <b>740</b>A and <b>740</b>B are formed simultaneously, spacer <b>733</b>B of interconnection element <b>740</b>A and body <b>745</b>A of interconnection element <b>740</b>B may be patterned and formed simultaneously. It is to be appreciated that, according to this method, spacer <b>733</b>B will be formed through the same multiple pattern masking, seeding, deposition, and planarization steps as body <b>745</b>A. Thus, spacer <b>733</b>B will be a composite of seed material and conductive material.

0197Spacers <b>732</b>A and <b>732</b>B may be patterned in the same masking material layer (e.g., a masking material layer patterned after seeding an area over body <b>745</b>A and an area corresponding to subsequently formed body <b>745</b>B). Spacers <b>732</b>A and <b>732</b>B are optional and can be reduced in size to provide, in one aspect, clearance as the interconnection elements are deflected. To the extent they are present, spacers <b>732</b>A and <b>732</b>B may be formed of the same conductive material deposition. Spacer <b>731</b>A is patterned and formed at the same time as body <b>745</b>B of interconnection element <b>740</b>B. According to this method, spacer <b>731</b>A will be formed through the same multiple pattern masking, seeding, deposition, and planarization steps as body <b>745</b>B. Thus, spacer <b>731</b>A will be a composite of seed material and conductive material.

0198In this embodiment, using photolithographic techniques, the length of the rectangularly-shaped body <b>745</b>A and <b>745</b>B of adjacent interconnection elements <b>740</b>A and <b>740</b>B, respectively, may be varied. Adjacent interconnection elements <b>740</b>A and <b>740</b>B are fabricated along the same axis (e.g., x-axis) at their posts (post <b>730</b>A and <b>730</b>B) and along a second axis (e.g., y-axis) at their tip structures (tip structures <b>760</b>A and <b>760</b>B). As noted, body <b>745</b>A of interconnection element <b>740</b>A is patterned directly over post <b>730</b>B of interconnection element <b>740</b>B. Accordingly, in an x-direction, the posts (<b>730</b>A and <b>730</b>B) are axially aligned. At the tip structure of each interconnection element (<b>760</b>A and <b>760</b>B), interconnection elements <b>740</b>A and <b>740</b>B are axially aligned along a y-axis. Thus, <figref idref="DRAWINGS">FIGS. 21(</figref><i>a</i>) and <b>21</b>(<i>b</i>) show adjacent interconnection elements that have a greater pitch between their tip structures than their posts. Such a configuration is suitable, for example, to generate an electronic component with a plurality of interconnection elements for probing a second electronic component having its contact pads or terminals arranged along its periphery and having an ultra-fine pitch. It is to be appreciated that the actual pitch between posts and tip structures according to this embodiment can vary to accommodate the pitch of contact pads or terminals on an electronic component to be contacted.

0199<figref idref="DRAWINGS">FIG. 21(</figref><i>c</i>) and <figref idref="DRAWINGS">FIG. 21(</figref><i>d</i>) describe a second orientation of adjacent interconnection elements according to an embodiment of the invention. Interconnection element <b>840</b>A includes post <b>830</b>A, body <b>845</b>A, and tip structure <b>860</b>A. Interconnection element <b>840</b>A also includes spacers <b>831</b>A and <b>832</b>A formed over post <b>830</b>A. Spacers <b>831</b>A and <b>832</b>A, in this example, separate body <b>845</b>A from underlying interconnection element <b>840</b>B. In one embodiment, the spacer is designed so the springs remain separate throughout a range of simultaneous displacement. Interconnection element <b>840</b>B includes post <b>830</b>B, body <b>845</b>B, and tip structure <b>860</b>B. Interconnection element <b>840</b>B further includes spacers <b>832</b>B and <b>833</b>B that align tip structure <b>860</b>B with tip structure <b>860</b>A of interconnection element <b>840</b>A along a z-axis (similar height). In <figref idref="DRAWINGS">FIGS. 21(</figref><i>c</i>) and <b>21</b>(<i>d</i>), interconnection elements <b>840</b>A and <b>840</b>B are axially aligned at both their posts and their tip structures.

0200Using photolithographic techniques, the rectangularly-shaped body of each of the adjacent interconnection elements in <figref idref="DRAWINGS">FIGS. 21(</figref><i>c</i>) and <b>21</b>(<i>d</i>) is fabricated to approximately the same length and the resulting interconnection element is offset by the distance between the posts along the same axis. Such a configuration is suitable, for example, to generate an electronic component with a plurality of interconnection elements for probing a second electronic component having its contact pads or terminals arranged in an ultra-fine pitch row along a center line thereof. Again, it is to be appreciated that the actual pitch between posts and tip structures according to this embodiment can vary to accommodate the pitch of contact pads or terminals of an electronic component to be contacted.

0201<figref idref="DRAWINGS">FIG. 21(</figref><i>e</i>) and <figref idref="DRAWINGS">FIG. 21(</figref><i>f</i>) illustrate still further arrangements using similar overlaying patterning techniques for forming interconnection elements as described with reference to <figref idref="DRAWINGS">FIGS. 21(</figref><i>a</i>)-<b>21</b>(<i>d</i>). <figref idref="DRAWINGS">FIG. 21(</figref><i>e</i>) shows a plurality of interconnection elements formed according to the techniques described hereinabove, arranged on an electronic component (not shown). Interconnection elements <b>900</b>A, <b>900</b>B, <b>900</b>C, and <b>900</b>D are arranged so that their corresponding tip structures <b>960</b>A, <b>960</b>B, <b>960</b>C, and <b>960</b>D, respectively, are aligned in a y-direction while posts <b>930</b>A, <b>930</b>B, <b>930</b>C, and <b>930</b>D are staggered in an x-direction. <figref idref="DRAWINGS">FIG. 21(</figref><i>f</i>) shows a second configuration wherein a plurality of interconnection elements <b>980</b>A, <b>980</b>B, <b>980</b>C, and <b>980</b>D are arranged on an electronic component (not shown) so that their corresponding tip structures <b>985</b>A, <b>985</b>B, <b>985</b>C, and <b>985</b>D, respectively are staggered in an x-y direction as are their corresponding posts <b>990</b>A, <b>990</b>B, <b>990</b>C, and <b>990</b>D, respectively. In this example, respective posts are larger (have a greater xy profile) than the tip structures in this embodiment.

0202The methods of forming interconnection elements described above using lithographic techniques including multiple masking and planarization steps should not be interpreted as limiting the scope of the invention. It is to be appreciated, that there are other ways of forming interconnection elements to accommodate, for example, dense contact pad or terminal arrays of electronic component device geometries. The lithographic formation including planarization steps described above permit the consistent formation of interconnection elements, including cantilever spring interconnection elements, having similar size and mechanical (e.g., compliance) properties. It is to be appreciated, however, that there may be other ways of forming interconnection elements, including multiple leaf portion interconnection elements that are suitable for the applications contemplated by the invention.

0000D. Exemplary Body Portions of Spring Interconnect Structures

0203The above description of forming interconnection elements of the invention is related generally to the formation of cantilever spring interconnection elements having a generally rectangular body with multiple leaf portions. It is to be appreciated, that the invention is not limited to interconnection elements having generally rectangular bodies. <figref idref="DRAWINGS">FIGS. 22(</figref><i>a</i>)-<b>23</b>(<i>b</i>) show various representative, useful configurations for leaf portions of the body of an interconnection element formed, for example, on sacrificial substrate <b>110</b>. It is to be appreciated that there may be various other configurations suitable for particular applications for the interconnection elements of the invention. <figref idref="DRAWINGS">FIGS. 22(</figref><i>a</i>)-<b>23</b>(<i>b</i>) are to be viewed as representative of these various configurations. Like reference numerals from the structure formed in <figref idref="DRAWINGS">FIGS. 7-17(</figref><i>e</i>) are used to indicate like components and/or materials where appropriate. It is also to be appreciated that, certain properties of an interconnection element adopting leaf portions having one or more of these alternative configurations, will differ from the rectangular beam structure described above. For example, in calculating the maximum stress under load of the tapered structures illustrated in <figref idref="DRAWINGS">FIG. 22(</figref><i>a</i>) through <figref idref="DRAWINGS">FIG. 22(</figref><i>g</i>), the width of the leaf portion should be considered.

0204<figref idref="DRAWINGS">FIG. 22(</figref><i>a</i>)-<b>22</b>(<i>g</i>) show top planar views of various configurations of a leaf portion of an interconnection element formed on substrate <b>110</b> in an xy plane. <figref idref="DRAWINGS">FIG. 22(</figref><i>a</i>) shows, for example, first body material <b>155</b><i>a </i>configured to have a taper in the y-direction (“y-taper”) as the material laterally extends (in an x-direction) from an area over the surface of, for example, second tip material <b>140</b>. This configuration more evenly distributes the stress on the interconnection element by reducing the size of the extremity of the leaf portion (e.g., the cantilever body) of the interconnection element. In <figref idref="DRAWINGS">FIG. 22(</figref><i>a</i>), a laterally extending portion of first body material <b>155</b><i>a </i>is depicted with substantially linear edges. It is to be appreciated that the edges need not be substantially linear but may be curved such as, for example, in a concave manner. <figref idref="DRAWINGS">FIG. 22(</figref><i>b</i>) shows laterally extending first body material <b>155</b><i>b </i>with substantially convex edges. The patterning of the masking material layer, such as first masking material layer <b>135</b>, dictates the shape of the leaf portion.

0205<figref idref="DRAWINGS">FIG. 22(</figref><i>c</i>) shows a third configuration of a leaf portion of an interconnection element in accordance with a first embodiment of the invention. In this configuration, first body material <b>155</b><i>c </i>extends laterally (in an x-direction) and transversely (in a y-direction) from, for example, second tip material <b>140</b> to form a curved leaf portion. <figref idref="DRAWINGS">FIGS. 22(</figref><i>d</i>) and <b>22</b>(<i>e</i>) show a fourth and a fifth configuration, respectively, where a leaf portion <b>155</b><i>d </i>and <b>155</b><i>e</i>, respectively, extend laterally and transversely. The laterally and transversely extending leaf portions may be desirous, for example, when fabricating interconnection elements to particularly minimize the pitch between adjacent interconnection elements. <figref idref="DRAWINGS">FIG. 22(</figref><i>f</i>) shows a sixth configuration of a leaf portion wherein first body material <b>155</b><i>f </i>partially encircles second tip material <b>140</b>. <figref idref="DRAWINGS">FIG. 22(</figref><i>g</i>) shows a seventh configuration of a leaf portion having an “S” shape in an xy plane. Again, the patterning of the masking material layer will dictate the shape of leaf portion of first body material <b>155</b><i>g. </i>

0206<figref idref="DRAWINGS">FIG. 23(</figref><i>a</i>) and <figref idref="DRAWINGS">FIG. 23(</figref><i>b</i>) show eighth and ninth configurations, respectively, of a leaf portion of the interconnection element in accordance with an embodiment of the invention in an xz plane. <figref idref="DRAWINGS">FIG. 23(</figref><i>a</i>) shows first body material <b>155</b><i>g </i>having a planar upper surface and a concave lower surface. <figref idref="DRAWINGS">FIG. 23(</figref><i>b</i>) shows first body material <b>155</b><i>h </i>having a planar superior surface and a linearly increasing inferior surface toward the extremity to form a beveled leaf portion. First body materials <b>155</b><i>g </i>and <b>155</b><i>h </i>can be formed in this manner in a number of ways, including varying the light source to shape the underlying and adjacent photoresist that forms the masking material and electroplating in the presence of a resistive layer mask to distribute the electroplated material where desired.

0207The above description relates primarily to interconnection elements having a body of cantilever leaf portions of similar dimension. It is to be appreciated that other configurations for the leaf portions are contemplated. The following figures are representative of the various configurations contemplated by the invention. Each of the different configurations may be formed using the formation techniques described above with reference to <figref idref="DRAWINGS">FIGS. 7-17(</figref><i>e</i>) with variations in one or more of the masking layer patterning, the body layer depositions, and the planarization steps.

0208<figref idref="DRAWINGS">FIG. 24(</figref><i>a</i>) and <figref idref="DRAWINGS">FIG. 24(</figref><i>b</i>) illustrate an embodiment of an interconnection element having a body of leaf portions of various dimensions. In <figref idref="DRAWINGS">FIG. 24(</figref><i>a</i>), interconnection element <b>1800</b> includes post <b>1810</b>, body <b>1805</b>, and tip structure <b>1815</b>. Body <b>1805</b> includes four leaf portions <b>1801</b>, <b>1802</b>, <b>1803</b>, and <b>1804</b>. In this embodiment, the length and the thickness of each leaf portion is varied. Thus, the length of leaf portion <b>1801</b>, “l₁,” is shorter than the length of second leaf portion <b>1802</b>, “l₂,” which is shorter than the length of leaf portion <b>1803</b>, “l₃,” which is shorter than the length of leaf portion <b>1804</b>, “l₄.” The thickness of first leaf portion <b>1801</b>, “t₁,” is similarly less than the thickness of second leaf portion <b>1802</b>, “t₂,” which has a material stress less than the maximum stress for a desired deflection distance, and is less than the thickness of third leaf portion <b>1803</b>, “t₃,” which is less than the thickness of fourth leaf portion <b>1804</b>, “t₄.” <figref idref="DRAWINGS">FIG. 24(</figref><i>b</i>) shows interconnection element <b>1800</b> subjected to a force at tip structure <b>815</b> and illustrates the compliance of body <b>1805</b>. An opposite configuration (i.e., shorter is thicker) is also contemplated for the situation where a similar spring constant is desired among the leaf portions.

0209<figref idref="DRAWINGS">FIG. 25(</figref><i>a</i>) and <figref idref="DRAWINGS">FIG. 25(</figref><i>b</i>) show another alternative configuration for the interconnection element of the invention. In <figref idref="DRAWINGS">FIG. 25(</figref><i>a</i>), interconnection element <b>1820</b> includes post <b>1822</b>, tip structure <b>1823</b>, and body <b>1825</b>. Body <b>1825</b> includes four leaf portions <b>1821</b><i>a</i>, <b>1821</b><i>b</i>, <b>1821</b><i>c</i>, and <b>1821</b><i>d </i>of similar length each having a proximal and a distal end. Tip structure <b>1823</b> is coupled at the distal end of superiorly-located leaf portion <b>1821</b><i>a</i>. Post <b>1822</b> is coupled at the distal end of inferiorly-located leaf portion <b>1821</b><i>d</i>. Supports <b>1824</b> coupled the adjacent leaf portions staggers between either the proximal end or the distal end of adjacent leaf portions. <figref idref="DRAWINGS">FIG. 25(</figref><i>b</i>) shows the interconnection element of <figref idref="DRAWINGS">FIG. 25(</figref><i>a</i>) with a force applied at tip structure <b>1823</b>. The deflection of interconnection element <b>1820</b> will generally not result in significant wiping of a contact pad or terminal.

0210<figref idref="DRAWINGS">FIG. 26(</figref><i>a</i>) and <figref idref="DRAWINGS">FIG. 26(</figref><i>b</i>) show yet another configuration for the interconnection element of the invention. In <figref idref="DRAWINGS">FIG. 26(</figref><i>a</i>), interconnection element <b>1830</b> includes post <b>1832</b>, tip structure <b>1833</b>, and body <b>1835</b>. Body <b>1835</b> includes three leaf portions <b>1831</b><i>a</i>, <b>1831</b><i>b</i>, and <b>1831</b><i>c </i>separated by supports <b>1834</b>. In this configuration, tip structure <b>1833</b> is aligned with post <b>1832</b>. The individual length of leaf portion <b>1831</b><i>b </i>is greater than either leaf portion <b>1831</b><i>a </i>or leaf portion <b>1831</b><i>b</i>. <figref idref="DRAWINGS">FIG. 26(</figref><i>b</i>) shows the interconnection element of <figref idref="DRAWINGS">FIG. 26(</figref><i>a</i>) with a force applied at tip structure <b>1833</b>. The deflection of interconnection element <b>1830</b> will generally not result in significant wiping of a contact pad or terminal.

0211<figref idref="DRAWINGS">FIG. 27(</figref><i>a</i>) and <figref idref="DRAWINGS">FIG. 27(</figref><i>b</i>) show another embodiment of the interconnection element of the invention. <figref idref="DRAWINGS">FIG. 27(</figref><i>a</i>) shows interconnection element <b>1830</b> including post <b>1832</b>, tip structure <b>1833</b>, and body <b>1835</b>. Body <b>1835</b> includes, in this case, two leaf portions. Each leaf portion is coupled to the adjacent leaf portion by supports <b>1834</b> and <b>1836</b> at a proximal end and at a distal end, respectively. The thickness of the superiorly-located leaf portion is greater than the thickness of the inferiorly-located leaf portion (t₁>t₂). <figref idref="DRAWINGS">FIG. 27(</figref><i>b</i>) shows the structure of <figref idref="DRAWINGS">FIG. 27(</figref><i>a</i>) after subjecting the interconnection element to a force at tip structure <b>1833</b>. <figref idref="DRAWINGS">FIG. 27(</figref><i>b</i>) shows that the inferiorly-located leaf portion of body <b>1835</b> buckles at point <b>1837</b> in response to the force applied at tip structure <b>1833</b>. In this embodiment, the buckling is facilitated by the inferiorly-located leaf portion having a thickness less than the other leaf portion of body <b>1835</b>. The buckling action may permit a reduction in the number of leaf portions necessary to achieve a desired deflection for a unit force. With this configuration, the wiping of the interconnection element against a contact pad or terminal in response to a force applied to the tip structure of interconnection element <b>1830</b> may be less than a cantilever configuration.

0212<figref idref="DRAWINGS">FIG. 28(</figref><i>a</i>) and <figref idref="DRAWINGS">FIG. 28(</figref><i>b</i>) show still another configuration for an interconnection element of the invention. In <figref idref="DRAWINGS">FIG. 28(</figref><i>a</i>), interconnection element <b>1840</b> includes post <b>1842</b>, tip structure <b>1843</b>, and body <b>1835</b>. Body <b>1835</b> includes, in this case, three leaf portions <b>1846</b>, <b>1847</b> and <b>1848</b>. The superior and inferior surfaces of the leaf portions may be a rectangular beam, including squares, with or without an opening therethrough. Adjacent leaf portions are separated by supports <b>1849</b>. Supports <b>1849</b> are arranged in staggered fashion between adjacent leaf portions. <figref idref="DRAWINGS">FIG. 28(</figref><i>b</i>) shows interconnection element <b>1840</b> with a force applied at tip structure <b>1843</b>. <figref idref="DRAWINGS">FIG. 28(</figref><i>b</i>) shows that the staggeredly-coupled leaf portions bow in opposite directions resulting in no wiping of the tip structure of the interconnection element against a contact pad or terminal.

0213<figref idref="DRAWINGS">FIGS. 29(</figref><i>a</i>)-<b>29</b>(<i>d</i>) illustrate a further embodiment of an interconnection element according to the invention. <figref idref="DRAWINGS">FIG. 29(</figref><i>a</i>) shows a planar side view, <figref idref="DRAWINGS">FIG. 29(</figref><i>b</i>) a second planar side view, and <figref idref="DRAWINGS">FIG. 29(</figref><i>c</i>) shows a perspective top view of interconnection element <b>1850</b> having post <b>1852</b>, tip structure <b>1853</b>, and body <b>1855</b>. In this embodiment, body <b>1855</b> includes four leaf portions <b>1856</b>, <b>1857</b>, <b>1858</b>, and <b>1859</b> that are each cylindrical leaf portions having, with the exception of leaf portion <b>1856</b>, an opening therethrough. The cylindrically-shaped leaf portions are coupled to one another through staggered supports <b>1854</b>. It is to be appreciated that the individual masking material layers may be modified to pattern cylindrical leaf portions as well as staggered supports or coupling. <figref idref="DRAWINGS">FIG. 29(</figref><i>d</i>) shows interconnection element <b>1850</b> having a force applied at tip structure <b>1853</b>. <figref idref="DRAWINGS">FIG. 29(</figref><i>d</i>) schematically illustrates the deformation of the leaf portions in response to a force applied at tip structure <b>1853</b> of body <b>1855</b> resulting in no wiping against a contact pad or terminal. Unlike interconnection elements having a plurality of cantilever leaf portions, there generally is no “travel-to-contact” component whereby a displaced leaf portion travels a distance to contact an adjacent leaf portion. Instead, an interconnection element of a plurality of cylindrical leaf portions behaves like a coil spring in that the leaf portions will continuously deform until the leaf portions strike one another at a maximum deflection.

0214It is to be appreciated that a cylindrical or other leaf portion may or may not have an opening therethrough. In the situation where an opening is desired, the opening may or may not be circular. <figref idref="DRAWINGS">FIG. 30</figref> shows leaf portion <b>1855</b> with a “clover-leaf” opening therethrough.

0215In general, the behavior of interconnection elements having stacked cylindrical leaf portions is different than the behavior of interconnection elements having layered cantilever leaf portions described above. Each cylindrical leaf portion has a spring constant, k, and a deflection to reach maximum stress. The spring constant of the stacked cylindrical interconnection element is determined by the spring constant of an individual leaf portion (k=k_leaf) and the maximum deflection is determined by the deflection distance of the total number of individual leaf portions: σ_max=n·δ_leaf, where n is the number of leaf portions. This differs, for example, from a stacked rectangular leaf portion like that of <figref idref="DRAWINGS">FIG. 3</figref> (e.g., cantilever) interconnection element where the spring constant is determined by the number of leaf portions (k=n·k_leaf) and the maximum stress by the deflection distance of a leaf portion: σ_max=δ_leaf.

0216<figref idref="DRAWINGS">FIG. 31</figref> illustrates still a further embodiment, where leaf portion <b>1870</b> of a body of interconnection element is “H”-shaped with supports <b>1875</b> patterned at diagonals from one another. Such a pattern will tend to stress the material by working the middle portion of the “H”-shape in a torsional manner, in response to a load or force applied to the interconnection element. The reduction in stress will permit a reduction in the number of leaf portions necessary for a desired deflection. <figref idref="DRAWINGS">FIG. 32</figref> shows leaf portion <b>1880</b> having a rectangular configuration with an opening therethrough and support portions <b>1885</b> at diagonals. It is to be appreciated that there are many other configurations in addition to the ones described above. Accordingly, the examples of interconnection elements and leaf portions described should be regarded in an exemplary rather than a restrictive sense.

0000E. Alternative Applications of Spring Interconnect Structures

0217In addition to the uses of the interconnection element of the invention as an interconnection element between two electronic components, <figref idref="DRAWINGS">FIGS. 33(</figref><i>a</i>)-<b>33</b>(<i>c</i>) show an embodiment where adjacent interconnection elements form a switch, e.g., a micro-switch, or a detector. <figref idref="DRAWINGS">FIG. 33(</figref><i>a</i>) shows a side view of adjacent interconnection elements <b>1905</b> and <b>1915</b>. <figref idref="DRAWINGS">FIG. 33(</figref><i>b</i>) is a top perspective view of interconnection elements <b>1905</b> and <b>1915</b>. <figref idref="DRAWINGS">FIG. 33(</figref><i>c</i>) is a top view of interconnection elements <b>1905</b> and <b>1915</b>.

0218Interconnection element <b>1905</b> includes post <b>1925</b> coupled to contact pad or terminal <b>1930</b> on electronic component <b>1900</b>. Interconnection element <b>1905</b> also includes spring <b>1910</b> of a plurality (e.g., three) of leaf portions coupled to post <b>1925</b>. The inferior leaf portion includes laterally extending tab portion <b>1950</b>.

0219Interconnection element <b>1915</b> includes post <b>1930</b> coupled to contact pad or terminal <b>1940</b> on electronic component <b>1900</b>. Interconnection element <b>1915</b> also includes body <b>1920</b> of, in this example, a single beam, coupled to post <b>1930</b>.

0220Interconnection element <b>1905</b> and interconnection element <b>1915</b> may be formed according to techniques described above, for example, with regard to the formation of interconnection elements according to <figref idref="DRAWINGS">FIGS. 21(</figref><i>a</i>)-<b>21</b>(<i>d</i>) and the accompanying text. Modifications regarding masking material openings and body (e.g., conductive) material deposition are accommodated to account for the alignment of the interconnection elements on electronic component <b>1900</b>, for tab portion <b>1950</b> of interconnection element <b>1905</b>, and for the differences in body portions of the respective interconnection elements. Such modifications will be understood by those of ordinary skill in the art based on the teachings discussed above and are therefore not presented herein.

0221Interconnection element <b>1905</b> and interconnection element <b>1915</b> have been illustrated and described without a tip structure. The embodiment described with reference to <figref idref="DRAWINGS">FIGS. 33(</figref><i>a</i>)-<b>33</b>(<i>c</i>), as with the other embodiments of interconnection elements described herein, does not require a tip structure to function. The tip structure in other embodiments defined herein offers one contact point for the interconnection element. It is to be appreciated that this contact point need not be established by the interconnection element, but can be established by an external source such as an electronic component or other substrate or structure contacting the interconnection element. For example, a contact point may be in the form of a traditional pad, a post, a pointed post, or other structure.

0222Referring to <figref idref="DRAWINGS">FIGS. 33(</figref><i>a</i>)-<b>33</b>(<i>c</i>), tab portion <b>1950</b> laterally extends from body <b>1910</b>. Tab portion <b>1950</b> is separated from a superior surface of body <b>1920</b> of interconnection element <b>1915</b> by a distance, lc.

0223When a force, F, is applied to the superior surface of body <b>1910</b>, body <b>1910</b> is deflected toward the surface of electronic component <b>1900</b>. Initially body portion <b>1910</b><i>a </i>is deflected. Body portion <b>1910</b><i>a </i>contacts body portion <b>1910</b><i>b </i>and deflects body portion <b>1910</b><i>b </i>toward electronic component <b>1900</b>. Further deflection causes body portion <b>1910</b><i>b </i>to contact body portion <b>1910</b><i>c </i>and deflect body portion <b>1910</b><i>c </i>toward electronic component <b>1900</b>.

0224Tab portion <b>1950</b> extends from body portion <b>1910</b><i>c </i>and is adapted to contact the superior surface of body <b>1920</b> upon sufficient deflection of body portion <b>1910</b><i>c</i>. The contacting of tab portion <b>1950</b> with a superior surface of body <b>1920</b> acts, in one sense, as a switch to, for example, close a circuit between the interconnection elements. Alternatively, the electrical interconnection between adjacent bodies <b>1910</b> and <b>1920</b> may be used to detect a capacitance between two electrodes. The capacitance can be correlated to a distance.

0225In one case, body <b>1920</b> may be fairly rigid and the deflection of tab portion <b>1950</b> onto body <b>1920</b> does not cause body <b>1920</b> to significantly deflect toward the surface of substrate <b>1900</b>. This is shown in the embodiment illustrated in <figref idref="DRAWINGS">FIGS. 33(</figref><i>a</i>)-<b>33</b>(<i>c</i>) wherein body <b>1920</b> of interconnection element <b>1915</b> is more robust, particularly in the z-direction, than the leaf portions of body <b>1910</b> of interconnection element <b>1905</b>. The deflection of body <b>1910</b> toward the surface of substrate <b>1900</b> may be limited by, for example, a travel stop. Alternatively, body <b>1920</b> of interconnection element <b>1915</b> may deflect toward the surface of substrate <b>1900</b> in response to a force such as a force applied by tab portion <b>1950</b> of interconnection element <b>1905</b>. In such case, body <b>1920</b> of interconnection element <b>1915</b> may be comprised of a plurality of leaf portions. Finally, body <b>1920</b> may itself include a tab portion to, upon deflection, contact another interconnection element or a terminal, for example, to close a circuit. In this manner, a device such as a tiered-relay may be formed.

0226In the above embodiment, mechanical and electrical contact was established between two adjacent interconnection elements. It is to be appreciated that mechanical and electrical contact may also be established in one interconnection element so that the interconnection itself acts as a switch. One way this may be accomplished is forming an interconnection element similar to the interconnection elements described above with reference to <figref idref="DRAWINGS">FIGS. 7-17</figref><i>e </i>and the accompanying text and electrically isolating one or more leaf portions of the interconnection elements. The application of a force to the body of the interconnection element will cause the isolated leaf portion(s) to contact other leaf portions and electrical contact.

0000F. Alternative Fabrication Techniques of a Multi-Leaf or Multi-Tier Spring Interconnection Element

0227<figref idref="DRAWINGS">FIGS. 34-52</figref> illustrate a second fabrication technique of forming a multiple leaf portion spring interconnection structure. As the starting point for this embodiment, a structure similar to the structure shown in <figref idref="DRAWINGS">FIG. 10</figref> is presented. <figref idref="DRAWINGS">FIG. 34</figref> shows structure <b>2110</b> that is, for example, a sacrificial substrate such as a semiconductor substrate. Substrate <b>2110</b> has a pyramidally-shaped depression formed therein as an outline for a portion of a tip structure to be formed. Overlying the surface of substrate <b>2110</b> is release layer <b>2125</b> of, for example, a metal such as aluminum deposited to a thickness of approximately 5,000 angstroms using conventional deposition techniques. Overlying release layer <b>2125</b> on the surface of substrate <b>2110</b> is seed layer <b>2130</b>. Seed layer <b>2130</b> is, for example, copper, palladium, or titanium-tungsten that establishes an appropriate potential for an electrolytic process. Overlying seed layer <b>2130</b> is first masking material layer <b>2135</b>. First masking material layer <b>2135</b> is, for example, a photopolymer (e.g., a negative photoresist) introduced onto the surface of substrate <b>2110</b> to a thickness of the desired height of a tip structure of an interconnection element taking into consideration the possibility of planarizing a portion of first masking material <b>2135</b> with tip structure material. Approximately 1-4 mils (25-100 μm) is a useful height range. First masking material layer <b>2135</b> is patterned to have an opening over the pyramidally-shaped depression in substrate <b>2110</b>. Alternatively, first conductive material layer mask <b>2150</b> may be introduced as a plurality of traces, each trace corresponding to an area over substrate <b>2110</b> as well as the tip structure formed in substrate <b>2110</b> where a body of an interconnection element is to be formed to serve, in one manner, as an electroform whereupon the body can be fabricated.

0228<figref idref="DRAWINGS">FIG. 34</figref> also shows tip structure material introduced onto substrate <b>2110</b>. Similar to the tip structure material described above with reference to <figref idref="DRAWINGS">FIG. 9</figref> and <figref idref="DRAWINGS">FIG. 10</figref> and the accompanying text, the tip structure material includes first tip material <b>2137</b> of, for example, palladium, gold, rhodium and their alloys, including, but not limited to, alloys of nickel and cobalt introduced to a thickness of about 1 to 5 μm or more—even tens of microns or more. Suitable introduction techniques include, but are not limited to, electroplating, chemical vapor deposition, sputter deposition, and electroless plating. The tip structure also includes second tip material <b>2140</b> of, for example, an alloy of nickel and cobalt introduced to a height approximating the height of first masking material layer <b>2135</b>.

0229<figref idref="DRAWINGS">FIG. 35</figref> shows structure <b>2000</b> after the removal of first masking material layer <b>2135</b>. In embodiment, wherein first masking material layer is a photoresist, first masking material layer <b>2135</b> may be removed by an etch, reactive ion etching, laser ablation, or wet etching.

0230<figref idref="DRAWINGS">FIG. 36</figref> shows structure <b>2000</b> after the introduction of first conductive material layer mask <b>2150</b>. First conductive material layer mask <b>2150</b> is, for example, a metal such as copper introduced by an electrolytic process. First conductive material layer mask <b>2150</b> is conformally introduced over the surface of substrate <b>2110</b>. First conductive material layer mask <b>2150</b> may be introduced by way of a blanket deposition over substrate <b>2110</b>. Alternatively, first conductive material layer mask <b>2150</b> may be introduced as multiple, non-contiguous regions or traces, each region corresponding to an area over substrate <b>2110</b> as well as the tip structure formed in substrate <b>2110</b> where a body of an interconnection element is to be formed to serve, in one manner, as an electroform whereupon the body can be fabricated.

0231<figref idref="DRAWINGS">FIG. 37</figref> shows structure <b>2000</b> after a planarization procedure such as a chemical-mechanical polish to planarize first conductive material layer mask <b>2150</b> and the tip structure. A planarization procedure establishes, in one aspect, the height of the tip structure.

0232<figref idref="DRAWINGS">FIG. 38</figref> shows structure <b>2000</b> after the introduction of second masking material layer <b>2160</b> serving as a pattern for a body portion, such as a leaf portion, of an interconnection element. Second masking material layer <b>2160</b> is, for example, a photopolymer such as a negative photoresist. <figref idref="DRAWINGS">FIG. 38</figref> also shows the introduction of first body material <b>2155</b><i>a </i>over surface of substrate <b>2110</b>. In one embodiment, first body material <b>2155</b><i>a </i>is a conductive material introduced by an electroplating process such as an electroplate alloy of nickel-cobalt. First body material <b>2155</b><i>a </i>is introduced to a thickness approximating the thickness of second masking material layer <b>2160</b>. It is to be appreciated that the amount deposited and the thickness of first body material <b>2155</b><i>a </i>will depend, in part, on the desired thickness of the particular leaf portion of the body of the interconnection element being formed.

0233<figref idref="DRAWINGS">FIG. 39</figref> shows structure <b>2000</b> after the removal of second masking material layer <b>2160</b>. In the embodiment where second masking material layer <b>2160</b> is a photoresist, the material may be removed by etch, laser ablation, or wet etching.

0234After the removal of second masking material layer <b>2160</b>, <figref idref="DRAWINGS">FIG. 40</figref> shows the introduction over the surface of substrate <b>2110</b> of second conductive material layer mask <b>2170</b>. In one embodiment, second conductive material layer mask <b>2170</b> is a material similar to first conductive material layer mask <b>2150</b>, such as copper introduced through an electrolytic process.

0235As shown in <figref idref="DRAWINGS">FIG. 41</figref>, after the introduction of second conductive material layer <b>2170</b> over substrate <b>2110</b>, first body material <b>2155</b> and second conductive material layer mask <b>2170</b> are planarized by way of, for example, a mechanical polish or a chemical-mechanical polish to form a leaf portion of an interconnection element on substrate <b>2110</b>. In one aspect, planarization of first body material <b>2155</b><i>a </i>and second conductive material layer mask <b>2170</b> establish the final thickness of the leaf portion of the body (i.e., control the final thickness of first body material <b>2155</b><i>s</i>).

0236<figref idref="DRAWINGS">FIG. 42</figref> shows structure <b>2000</b> after the introduction of third conductive material layer mask <b>2180</b>. In one embodiment, third conductive material layer mask <b>2180</b> is similar to first conductive material layer mask <b>2150</b> and second conductive material layer mask <b>2170</b> and is, for example, electroplated copper. In this embodiment, third conductive material layer mask <b>2180</b> is introduced to a thickness on the order of 0.1 to 5 μm. Third conductive material layer mask <b>2180</b> defines, in one aspect, a gap or opening between adjacent leaf portions of the interconnection element body.

0237<figref idref="DRAWINGS">FIG. 43</figref> shows structure <b>2000</b> after the patterning of third masking material layer <b>2190</b> over the surface of substrate <b>2110</b> and to have an opening to third conductive material layer mask <b>2180</b> at a point desired to be utilized as a support area between adjacent leaf portion of the interconnect element. In <figref idref="DRAWINGS">FIG. 43</figref>, third masking material layer <b>2190</b> is patterned at opening <b>2195</b> to expose an area portion of third conductive material layer mask <b>2180</b> at a proximal end of the structure relative to leaf portion of material <b>2155</b><i>a. </i>

0238<figref idref="DRAWINGS">FIG. 44</figref> shows structure <b>2000</b> after the removal of the exposed portion of third conductive material layer mask <b>2180</b>. In the example where third conductive material layer mask <b>2180</b> is copper, a wet chemical etching procedure may be used to remove the exposed copper.

0239After the removal of the exposed portion of third conductive material layer mask <b>2180</b>, <figref idref="DRAWINGS">FIG. 45</figref> shows structure <b>2000</b> after patterning third masking material layer <b>2190</b> a second time to have an opening corresponding with an opening for a desired second leaf portion of the body of an interconnect element. <figref idref="DRAWINGS">FIG. 46</figref> shows the structure introduction of second body portion material <b>2155</b><i>b </i>over the surface of substrate <b>2110</b> in the patterned opening of third masking material layer <b>2190</b>. In one example, second body material <b>2155</b><i>b </i>is similar to first body material <b>2155</b><i>a </i>(e.g., Ni—Co) and is introduced by an electrolytic process. As illustrated in <figref idref="DRAWINGS">FIG. 46</figref>, the leaf portion formed by first body material <b>2155</b><i>a </i>and second body material <b>2155</b><i>b </i>are separated by third conductive material layer mask <b>2180</b> with the exception of a support portion.

0240<figref idref="DRAWINGS">FIG. 47</figref> shows structure <b>2000</b> after the removal of third masking material layer <b>2190</b>. In the embodiment of third masking material layer <b>2190</b> is a photoresist, suitable removal methods are discussed above.

0241<figref idref="DRAWINGS">FIG. 48</figref> shows structure <b>2000</b> after the introduction of fourth conductive material layer mask <b>2210</b>. In one embodiment, fourth conductive material layer mask <b>2210</b> is similar to the previously introduced conductive material layer mask (e.g., copper) and is introduced by an electrolytic process.

0242<figref idref="DRAWINGS">FIG. 49</figref> shows structure <b>2000</b> after the planarization of fourth conductive material layer mask <b>2210</b> and second body material <b>2155</b><i>b</i>. The planarization step defines, in one aspect, the thickness of second body material <b>2155</b><i>b. </i>

0243<figref idref="DRAWINGS">FIG. 50</figref> shows structure <b>2000</b> after the repetition of the above operations to form three additional leaf portions and post <b>2200</b> utilizing alternative operations of pattern mask, conductive material layer mask, and planarization. <figref idref="DRAWINGS">FIG. 51</figref> shows structures to leave a free-standing interconnection element. In the embodiment where the various conductive layer mask are formed of copper, a wet chemical etch process, selected for copper may be utilized. <figref idref="DRAWINGS">FIG. 51</figref> shows structure <b>2000</b> including interconnect element having a tip structure coupled to a body portion of five leaf portions of first body material <b>2155</b><i>a</i>, second body material <b>2155</b><i>b</i>, third body material <b>2155</b><i>c</i>, fourth body material <b>2155</b><i>d</i>, and fifth body material <b>2155</b><i>e</i>. Coupled at a proximal end of leaf portion defined by fifth body material <b>2155</b><i>e</i>, is post <b>2200</b>. Following the removal of the conductive material layer masks, seed layer <b>2130</b> may be removed such as by an etching step as known in the art to expose release layer <b>2125</b>. <figref idref="DRAWINGS">FIG. 52</figref> shows the structure after the removal of the exposed release layer <b>2125</b>. At this point, the free-standing interconnection element may be transferred to, for example, an electronic component similar to the transfer described with respect to <figref idref="DRAWINGS">FIG. 17</figref><i>e </i>and the accompanying text.

0244In the above embodiment, an interconnection element is formed on a sacrificial substrate and then transferred to an electronic component. It is to be appreciated, that the techniques described in this embodiment of forming an interconnection element on a sacrificial substrate is again representative of one technique of forming the interconnection element of the invention. A second technique wherein the interconnection element is formed directly on an electronic component is also contemplated. Reference is made to patent application Ser. No. 09/205,022, filed Dec. 2, 1998, entitled “Lithographic Contact Elements,” and patent application Ser. No. 09/205,023, filed Dec. 2, 1998, entitled “Lithographic Contact Elements,” claimed by the assignee of the invention described herein which describe such a technique and are incorporated herein by reference.

0245Still another embodiment of fabricating the interconnection element of the invention may be accomplished utilizing a process described by Adam L. Cohen, in an article entitled “3-<i>D Micromachining by Electrochemical Fabrication</i>,” in the publication “Micromachine Devices,” Vol. 4, No. 3, March 1999 at pages 6-7. The article describes a selective electroplating process utilizing through-mask plating. Specifically, a conformable insulator is patterned directly on an anode and pressed against a substrate to establish the electroplating mask. After electroplating, the mask is separated from the substrate. In the instant invention, one use of the process described by the referenced article is to substitute the conformable insulated mask for the masking material layers and pattern the primary interconnection element components.

0246Various embodiments of the interconnection elements disclosed above are particularly suitable for making electrical connection with, for example, an electronic component having “fine-pitch” contact pads or terminals, for example, spacing of at least less than 5 mils (130 μm), such as 2.5 mils (65 μm). Applications to larger scale devices, including devices with contact pitches of about 50-100 mil (1.3-2.6 mm) and even larger are feasible as well.

0247In the preceding detailed description, the invention is described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.